What are the best unified APIs for ATS integrations?
Comparing seven ATS integration platforms, unified APIs and code-first platforms, on the dimensions that product and engineering leaders care about.
What are the best integration providers for ATS integrations?
What is a unified ATS API?
A unified ATS API is one set of endpoints and one data model to read and write recruiting data (jobs, candidates, applications, stages, interviews, offers and attachments) across many applicant tracking systems. You integrate once, and the provider handles authentication, partner access, schema normalization, and ongoing maintenance for every ATS in its catalog.
Buyers also call this category an ATS integration platform, a recruiting API, an ATS integration provider or ATS middleware. The terms overlap, so the next section breaks them down first.
What is the difference between a unified API, embedded iPaaS and middleware for ATS integrations?
A unified API normalizes many applicant tracking systems into one schema and maintains the connectors. Embedded iPaaS and workflow middleware orchestrate steps between systems but leave the ATS data modeling to you.
| Approach | Examples | What it solves | Where it breaks for ATS |
|---|---|---|---|
| Unified API | Kombo, Merge, Unified.to, Apideck, Knit | One normalized ATS schema, the vendor maintains connectors and partner access | You inherit the vendor's data model and its sync architecture, so check both per system |
| Code-first integration platforms | Nango, Ampersand | Full control over models and sync logic, in your git repo | You implement and maintain every ATS mapping, write path and partner relationship yourself |
| Embedded iPaaS / middleware | Workato Embedded, Paragon, Prismatic, Tray Embedded | Customer-facing workflow builders and orchestration | Solves orchestration, not normalization. You still model Greenhouse vs. Workday Recruiting vs. iCIMS stages and dispositions per connector |
| Apply and job-distribution middleware | JobSync | Managed apply flows and job distribution into enterprise ATS | Built around getting applicants into the ATS, not a general read and write recruiting API for your product |
ATS integrations come with two problems that sit underneath the plumbing. One is normalization. Every ATS models stages, outcomes and rejection reasons differently, and every customer configures them differently again. The other is newer, and it’s around access. Greenhouse requires a signed partnership for Harvest v3, Workday meters API calls, and SAP throttles SuccessFactors tenants. A unified API is worth it when it takes both problems off your plate.
How should you read this unified ATS API comparison?
Kombo builds a unified API for people data, so we have an interest in the outcome. We aimed to keep it valuable and objective by stating plainly where Kombo is the wrong choice and date-stamping the page so you can see how current the numbers are. All information here comes from each provider’s public website and documentation, as of October 13, 2026. Integration counts are the ATS connectors in each provider’s own public catalog on that date, excluding deprecated connectors, sandbox or test connectors, and duplicate listings of the same system. If we couldn’t confirm a competitor fact on the provider’s own site or docs, we left it out.
On that note - we left StackOne and Bindbee out of this comparison. StackOne’s documentation lists its unified ATS API as legacy and no longer in active development, as the company now focuses on connectors for AI agents (StackOne docs). Bindbee lists 12 ATS integrations and is better known as an HRIS provider, which we covered in our HRIS comparison.
How should you evaluate a unified ATS API?
Technical product and engineering leaders tend to score ATS integration providers on six dimensions:
(1) Integration coverage and partner access: How many ATS integrations does the provider list, and do they cover the systems your customers run, including Workday Recruiting, SAP SuccessFactors Recruiting, Oracle Recruiting and iCIMS? Partnerships gate access to many ATS - Greenhouse Harvest v3 is partner-only, and iCIMS and Workday require partner agreements. A connector without the partnership support behind it may not get through your customer’s security review.
(2) Sync architecture, freshness and API footprint: Does the provider consume native webhooks, run scheduled syncs, read live on every request, or combine them? Does it detect deletions? Can it limit sync to the candidates your product touches, or to a recent time window? How does its API traffic against the customer’s ATS scale?
(3) Data model depth across read and write: Which objects can you read, patch, and write: jobs, candidates, applications, screening questions, stages, interviews, offers, notes, scorecards, attachments, and tags. Many use cases also care about disposition data and source attribution.
(4) Field mapping: Customers often keep critical data in custom fields and screening questions on candidates, applications and jobs. Can you select a field, rename it, transform it into the shape your product expects, and do that per customer?
(5) Developer experience and support: Sandbox availability for enterprise ATS, logs per sync and per write, automatic issue detection, SDKs, documentation quality, and whether support comes from the engineers who built the connector.
(6) Security, auditability and data minimization: Hosting regions, certifications, audit logs and field-level scopes. Candidate data is sensitive PII, so ask how much of it the provider holds at rest. A scoped sync that only covers the candidates your product created keeps far less PII in the integration layer than a full copy of the ATS.
Why are ATS vendors metering, gating and throttling API access in 2026?
One new trend emerging that’s worth considering is that the largest recruiting and HCM platforms have started putting limits and prices on third-party API traffic. Workday meters calls above an annual allowance, SAP throttles SuccessFactors tenants, Greenhouse requires a partner agreement to access their Harvest v3 API, and iCIMS and others charge for credentials. From what we’re hearing, more players are expected to follow.
If you sell into enterprise recruiting teams, these policies are starting to change how customers evaluate you. As IT admins start to review traffic load, an efficient sync architecture can become a differentiator against your competitors.
As of October 2026, Kombo has rebuilt its ATS syncs around this. Instead of re-walking the whole ATS on every run, candidate package sync first builds a lightweight index of every candidate, which needs only IDs and timestamps. It then fetches each candidate with their applications, interviews, notes and scorecards, newest first. Recently changed candidates are refreshed often, and older ones less frequently, down to about once a month for candidates untouched for a year. Kombo adjusts that schedule per integration, so you decide how to balance API load against freshness. Webhooks and delta syncs keep picking up changes in between.
For our design partners, this cuts their API calls by 50 to 60%, depending on the system and the data synced. Products that only need the candidates they create can cut traffic further with Kombo’s created-candidates-only mode (Kombo docs: tracking created applications). Alternatively, they can also limit a full sync to recent data with upstream filtering.
Should a unified ATS API use webhooks, scheduled sync or live pass-through?
For enterprise ATS, consume native webhooks where the ATS emits them, and run a scheduled delta sync to catch missed events and deletions. Bear in mind that webhook support varies by system - while Greenhouse, Lever and Ashby emit them, Workday doesn’t push events to third-party apps out of the box, SAP SuccessFactors does so only for a few Intelligent Services events the customer’s admin configures, and Bullhorn offers an event subscription you poll. On those systems, the scheduled delta sync does most of the work.
A pass-through approach reads the ATS on every call. That works for single-record lookups but breaks at enterprise scale in three ways:
(1) Upstream limits and latency become yours: SuccessFactors caps each tenant at 600 requests per minute, and at 50 per minute on candidate records, with hard 429 rejections for new tenants from January 2027. With pass-through, a throttled call fails inside your product’s request. Reads are also as slow as the ATS, which shows on Workday’s SOAP API and SuccessFactors OData when you page through a large candidate base. Some ATS cap reads harder still: SmartRecruiters allows one concurrent request on its candidate list endpoint (throttling policies), and iCIMS includes 10,000 API requests a day per customer (iCIMS integration terms).
(2) There is no stored state: Pass-through providers detect changes with “virtual” webhooks that poll the ATS on an interval. Without a stored copy, there is no deletion tracking and no last-known record when the ATS is down.
(3) API cost follows your reads: Every read and every poll counts against the customer’s API allowance, which Workday meters from February 2027. A stored sync spends allowance too, so ask any provider what drives its call count: your read volume, the size of the customer’s ATS, or only the records your product creates.
Pass-through is a good choice if you need to make a handful of calls and need the current record. Some buyers also require zero candidate data at rest. If that’s your buyer, a pass-through provider is a reasonable choice. The trade-off grows with instance size: on an ATS with millions of candidates, every full read pages through the ATS’s rate limits again, and Unified.to’s own option for heavy read volume is Database Sync, which writes the records into your database. But please carefully check which of your target systems it can detect changes on without polling, and what its polling interval costs on Workday.
Should you build Greenhouse, Workday, SAP SuccessFactors and iCIMS integrations yourself?
Only if integrations are core to your product and you have engineers to maintain them. Each of the four has its own API, its own access process and, increasingly, its own limits on third-party traffic.
| ATS | API | Access for a third-party product | Rate limits and metering | Change events |
|---|---|---|---|---|
| Greenhouse | Harvest API v3 (REST, OAuth 2.0). Harvest v1 and v2 were retired on August 31, 2026 | Partner OAuth requires a signed Greenhouse partnership agreement | No single published limit for v3 | Native webhooks, set up in the customer's Greenhouse account |
| Workday Recruiting | Workday Web Services (SOAP), Workday REST API and Reports-as-a-Service | Partner agreement, plus an integration system user in each customer's tenant | Annual allowance of 2.5 to 6.5 million production API calls by company size, and partner integrations count toward it. Calls above it draw Flex Credits from February 1, 2027 (Redress) | No webhooks for third-party apps |
| SAP SuccessFactors Recruiting | OData API v2 | API credentials set up by the customer's admin | 600 requests per minute per tenant and 50 per minute on Candidate. Hard 429s for new tenants from January 1, 2027 (Redress) | Intelligent Services events for a few recruiting events, configured by the customer's admin |
| iCIMS | iCIMS REST API | Partner agreement | 10,000 API requests a day per customer (iCIMS integration terms) | Event Notifications, configured per customer (iCIMS) |
A unified ATS API covers all four through one integration and handles the rate limits, partner requirements and per-customer stage mapping. On Greenhouse, you still sign the Harvest v3 partnership yourself, and Kombo refers you into the program.
How many ATS integrations does each provider offer?
As of October 13, 2026, Unified.to lists the most ATS integrations at 152, followed by Kombo at 108, Merge at 63, Knit at 40, Nango at 25, Apideck at 10 and Ampersand at 3.
| Provider (linked to its ATS catalog) | ATS integrations listed | Default architecture | Pricing model |
|---|---|---|---|
| Kombo | 108 | Scoped candidate sync, webhooks plus scheduled sync | Annual platform fee plus a flat fee per connected customer, not per API call or data volume (pricing) |
| Merge | 63 | Full scheduled sync | Per production Linked Account: first 3 free, then $650/month for up to 10 and $65 per additional Linked Account; Professional and Enterprise are contract-based (pricing) |
| Unified.to | 152 | Live pass-through | Usage-based on API requests, from $750/month for 750,000 calls with unlimited customer connections; webhook events count toward the monthly request limit (pricing) |
| Apideck | 10 | Live pass-through | Per active consumer: Launch from $599/month for 25 consumers, Scale from $1,299/month for 100, Enterprise custom (pricing) |
| Ampersand | 3 | Scheduled reads defined in amp.yaml | Priced on infrastructure consumption (read, write, subscribe, search and proxy actions), not per connection: startup program plus custom Growth and Enterprise plans (pricing) |
| Knit | 40 | Pass-through, webhook push | Start Up at $499/month; Scale Up and Enterprise on request; connected accounts contract-based (pricing) |
| Nango | 25 | Defined by you | Usage-based: free tier with 10 connections; pay-as-you-go from $50/month including $50 of credits, then $0.29 per connection plus compute and data transfer; Growth add-on at $450/month (pricing) |
Which are the best unified APIs for ATS integrations in 2026?
The leading unified APIs for ATS integrations in 2026 are Kombo, Merge, Unified.to, Apideck, Knit, Ampersand and Nango. Below is an assessment of each across the six dimensions product and engineering leaders score them on.
1. Kombo
Who is Kombo best for?
Kombo is best for AI screening, AI interviewing, assessment, sourcing, hiring-fraud, job board, and staffing products that sell into mid-market and enterprise customers in the US and EU, need deep write-back into the customer’s ATS, and need to keep their API footprint on that ATS small.
Which ATS systems does Kombo cover?
Kombo lists 108 ATS integrations in its ATS catalog as of October 13, 2026, including Workday, SAP SuccessFactors, Oracle Recruiting Cloud, iCIMS, SmartRecruiters, Greenhouse, Lever, Ashby, Workable, Teamtailor, Bullhorn, Avature, Phenom, Eightfold, Cornerstone OnDemand, Cornerstone TalentLink, UKG Pro and UKG Ready, plus European systems such as Softgarden, d.vinci, rexx systems and Personio.
Kombo holds certified partnerships with Workday, SAP SuccessFactors, Oracle, Greenhouse and UKG. A separate assessment API covers assessment and background-check modules on 18 ATS, including Workday, SAP SuccessFactors, Oracle Recruiting Cloud, iCIMS, Greenhouse and Lever (assessment connectors). If your customer can’t get you API credentials, AI Apply submits applications through the employer’s career site, as covered in the section on missing API access below.
How deep is Kombo’s ATS data model?
Kombo covers jobs, candidates, applications, application stages, screening questions, users, roles, tags, interviews, scorecards, offers, rejection reasons, attachments, result links and notes (Kombo ATS API). As of October 13, 2026, Kombo’s API reference lists creating applications on 103 of its 108 ATS integrations, attachment uploads on 57, screening-question answers on 56, stage moves on 52, result links on 47, notes on 44, and rejecting an application with a reason and a note on 24.
Applications return unified disposition data through outcome (PENDING, HIRED or DECLINED) on 79 ATS, which Kombo derives from whatever the ATS uses - stages, booleans, dates or statuses. Rejection reasons are readable on 28 ATS, and the reject endpoint takes a required reason and an optional note. Application attribution attaches your source to the applications you create automatically, after a one-time source setup on some ATS.
How does Kombo sync ATS data, and what does that mean for API traffic?
Kombo consumes native webhooks where available, including Greenhouse, Lever, Ashby, SmartRecruiters and Workable (upstream webhooks), runs a scheduled sync underneath to catch missed events and deletions, and sends you data-changed webhooks. The scheduled sync runs every three hours by default and down to five minutes on higher plans.
By default, Kombo syncs only the candidates and applications created through your integration, so API traffic scales with what your product creates (docs). Upstream filtering limits a full sync to records updated after a cutoff date or within a rolling window, best effort per ATS (docs), and a sync-all mode fetches every candidate, newest first (Kombo ATS API).
Kombo keeps this stored, scoped copy on purpose. A large ATS is read once, at the pace its rate limits allow, and after that Kombo fetches changes, so your product’s reads and searches never wait on the customer’s ATS.
Can Kombo map and transform custom fields?
Yes. Kombo exposes custom fields and integration fields on jobs, candidates and applications, returns the raw payload as remote data, and supports passthrough requests for system-specific endpoints. When you create candidates or applications, remote fields let you write extra data straight into each ATS’s own fields (custom fields). Advanced mappings let you write a TypeScript formula in the dashboard that transforms a value before it lands in your custom field, for example, combining a job’s description, benefits, and qualifications into one text. Transformations are set per integration, so your support team can change a mapping without a release.
How good is Kombo’s developer experience and support?
Kombo ships SDKs in TypeScript, Python and Ruby, a built-in Kombo Sandbox connector, and shared sandboxes for systems such as SAP SuccessFactors and Workday on the Scale and Enterprise plans. Observability covers five log types (sync, connection flow, action, pass-through and incoming webhook), kept for 30 days on Start and Scale and 90+ days on Enterprise (pricing). Data Explorer lets you search records and run any write action from the dashboard without code.
Kombo provides unlimited support on every plan through shared Slack or Microsoft Teams channels with the engineers who built the connectors, from offices in New York and Berlin and across West Coast, East Coast and European time zones.
How secure is Kombo?
Kombo holds SOC 2 Type II, ISO 27001 and HIPAA, and complies with GDPR (security). Customers choose a US, Canada, or EU data center, and each region runs on isolated infrastructure, so a US deployment processes candidate data only in the US. Field-level scopes set any field outside your scope to null during sync, so out-of-scope data is never stored.
Watch out
Kombo covers people data only: HRIS, ATS, LMS, payroll and assessment. If you need CRM, accounting or ticketing from the same vendor, Merge, Unified.to, Apideck, Knit, Ampersand or Nango fit better.
Which customers use Kombo for ATS integrations?
Indeed, Juicebox, Metaview, Paraform, Socure, TestGorilla
2. Merge
Who is Merge best for?
Merge is best for products that need ATS integrations alongside CRM, accounting, ticketing or file storage from one vendor, and that want a stored copy of the customer’s full ATS history.
Which ATS systems does Merge cover?
Merge lists 63 ATS integrations in its ATS catalog as of October 13, 2026, including Workday, SAP SuccessFactors, Oracle Recruiting, Oracle Taleo, iCIMS, SmartRecruiters, Greenhouse, Lever, Ashby, Workable, Teamtailor, Bullhorn, UKG Pro Recruiting, Cornerstone TalentLink and Infinite BrassRing. Avature, Phenom, and Eightfold are not listed. Merge is an official Workday partner at the Innovation Silver tier (Merge), but does not state its Greenhouse Harvest v3 partner status publicly.
How deep is Merge’s ATS data model?
Merge documents 17 ATS common models, including candidates, jobs, applications, interviews, scorecards, attachments, offers, screening questions, reject reasons and tags. As of October 13, 2026, Merge’s supported-fields matrix lists creating applications on 24 integrations, uploading attachments on 18, a writable application stage on 17, and screening-question answers and notes (as activities) on 9 each. Merge has no endpoint to reject an existing application, and a reject reason can be set when creating an application on 3 integrations (create application). Merge’s separate Agent Handler product offers per-system tools outside the unified model, such as a Greenhouse tool that rejects an application with a reason (Agent Handler Greenhouse connector).
How does Merge sync ATS data, and what does that mean for API traffic?
Merge copies and stores ATS data on a schedule, from daily on launch plan to customizable down to every five minutes on Professional and Enterprise (pricing, Greenhouse integration). On Professional and Enterprise, Merge can also consume the ATS’s own webhooks (third-party webhooks). Merge syncs everything by default. Selective Sync adds time-based filters for all customers, with the full set of custom filters on Enterprise, and filters only work where the underlying platform supports them (Selective Sync). API traffic scales with the size of the customer’s ATS.
Can Merge map and transform custom fields?
Merge offers field mapping integration-wide and per Linked Account on the Professional and Enterprise plans, and transforms remote data with JSONata in its advanced mapping (field mapping).
How good is Merge’s developer experience and support?
Merge offers mature, enterprise-grade tooling - searchable logs, automated issue detection with an Issues API (issue tracking), and endpoints for Linked Account token management. It ships SDKs in Node, Java, Python, Go, Ruby and C#, and offers sandboxes for some integrations on Professional and Enterprise. Log retention is 3 days on Launch, 30 days on Professional and 90+ days on Enterprise. Support is more limited though - it’s email on launch, email and chat on Professional, and a shared Slack channel only comes with the Enterprise plan (pricing).
How secure is Merge?
Merge holds SOC 2 Type II, ISO 27001 and HIPAA, and is GDPR compliant (trust center). Merge hosts in the US, EU and APAC and sells single-tenant and self-hosted deployments (security), and provides audit trails in the dashboard and via API.
Watch out
Merge’s default full sync means its API footprint grows with the customer’s ATS, which matters on metered Workday and throttled SuccessFactors tenants. ATS also doesn’t appear to be their focus anymore - between June and early October 2026, Merge’s changelog added one ATS integration to its unified API (AgileATS, read-only) and no new ATS write endpoints, while Agent Handler and Merge Gateway appeared in nearly every weekly entry (changelog).
Which customers use Merge for ATS integrations?
Fetcher, HireBeat, Scholars, Brighire by Zoom (Merge case studies)
3. Unified.to
Who is Unified.to best for?
Unified.to is best for products whose customers run small and mid-sized ATS instances, that need a broad ATS catalog alongside many other integration categories from one vendor, and whose buyers require that no candidate data is stored at rest.
Which ATS systems does Unified.to cover?
Unified.to lists 152 ATS integrations in its ATS catalog as of October 13, 2026, including Workday, SAP SuccessFactors, Oracle HCM, Oracle Taleo Business Edition, iCIMS, Avature, Phenom, Eightfold, Cornerstone, UKG Pro, Greenhouse, Lever, Ashby, SmartRecruiters and Bullhorn. Unified.to does not publish partnerships with Workday, SAP or Oracle, or its Greenhouse Harvest v3 partner status.
How deep is Unified.to’s ATS data model?
Unified.to models nine objects and publishes a per-integration capability matrix. As of October 13, 2026, that matrix lists writable candidate fields on 93 integrations, application fields on 63, activities on 53, documents on 44, interviews on 12 and scorecards on 11. Stage changes are writable on 46 systems through the application’s status fields, either a normalized status or the ATS’s own stage name in original_status, depending on the integration (Unified.to Greenhouse integration). Unified.to documents no rules for how a normalized status maps to a customer’s custom stages, and its own guide states that there is no global stage-transition model (Unified.to). rejected_reason is writable on 7 integrations, and there is no dedicated reject operation. Notes are modeled as activities of type NOTE (activity model), and offers are read-only inside the application object.
How does Unified.to sync ATS data, and what does that mean for API traffic?
Unified.to is live pass-through with no candidate data stored. Native ATS webhooks are passed through, and virtual webhooks detect changes by polling at a configurable interval down to every minute (virtual webhooks). Each poll is a call against the customer’s ATS, so traffic scales with your polling interval and read volume. Deletions are reported only where the integration supports them, and there is no last-known record during an ATS outage.
List calls return at most 100 records per page, and every page is a billable API call (pagination, pricing). One full read of a 5-million-candidate instance therefore takes 50,000 calls before applications, notes or attachments, and the next full read starts from scratch. Unified.to’s own guide says an initial load on a large instance “could take a very long time” (webhooks guide), and its Workday integration lists no filter or paging options for candidates (Workday integration).
Can Unified.to map and transform custom fields?
Unified.to supports custom fields through a metadata array on each object, managed through its Metadata API, and reads and writes raw payloads through raw fields (custom metadata guide). It does not document a transform layer or per-customer mapping configuration.
How good is Unified.to’s developer experience and support?
Unified.to ships SDKs in TypeScript, Python, PHP, Java, Go, C# and Ruby, pre-built authorization components for React, Angular, Vue, Svelte and plain JavaScript, and a sandbox environment with synthetic data (sandbox). Support runs through a private Slack or Discord channel on every paid plan, with 2 support hours a month on Grow, 5 on Pro and 15 on Scale, during US Eastern business hours (pricing).
How secure is Unified.to?
Unified.to holds SOC 2 Type II and states HIPAA and GDPR compliance (security), but does not hold ISO 27001 according to its own page (Unified.to). Data residency covers the US, EU, and AU (multi-region sync). While zero data at rest seems like a strong security argument, they still store your credentials, so treat this with a bit of caution.
Watch out
Stage changes run through status-field writes on 46 of Unified.to’s 152 integrations, with no documented mapping to the customer’s own stages. Rejection-reason writes cover 7, and Unified.to does not publish partnerships with Workday, SAP or Oracle, so check its matrix against the systems your customers run. Because every read and poll hits the customer’s ATS, API traffic and cost follow your read volume, your polling interval and the size of the customer’s instance, and webhook events count toward the monthly API request limit (pricing).
Which customers use Unified.to for ATS integrations?
HireTechLadies.com, Sailes.ai, Talin, Sync2Hire (listed on unified.to/ats)
4. Apideck
Who is Apideck best for?
Apideck is best for products whose main integration needs are accounting, HRIS or CRM, and that want ATS reads on systems such as Greenhouse, Lever, Workday and SAP SuccessFactors from the same vendor.
Which ATS systems does Apideck cover?
Apideck lists 10 ATS integrations (Apideck ATS connectors) as of October 13, 2026: Greenhouse, JobAdder, Lever, Tellent Recruitee, Sage HR, SAP SuccessFactors, Teamtailor, Workable, Workday and Bullhorn. iCIMS, Oracle Recruiting, SmartRecruiters and Ashby are not listed, and Apideck does not publish ATS partnerships.
How deep is Apideck’s ATS data model?
Apideck’s ATS API has three resources: jobs, applicants and applications (ATS API reference). Interviews, scorecards, offers, notes and attachments are not part of the model, beyond a CV URL field on applicants. Its coverage page lists the applications resource, in beta, on 4 of the 10 connectors, and application stage updates on Teamtailor only.
How does Apideck sync ATS data, and what does that mean for API traffic?
Every Apideck call hits the underlying ATS live. Virtual webhooks simulate change events by polling, typically every 24 hours, with the frequency depending on the plan (Apideck help center). Your read latency is the ATS’s latency, upstream rate limits become your rate limits, and virtual webhooks report created and updated records, not deletions.
Can Apideck map and transform custom fields?
Apideck lets your customers map custom fields in its Vault connection UI on the Scale and Enterprise plans (field mapping). It covers selecting and renaming but runs no transform logic.
How good is Apideck’s developer experience and support?
Apideck ships SDKs in TypeScript, Python, PHP, Java, Go and C#, plus a CLI (SDKs). Connectors use Apideck’s sandbox OAuth apps by default, logs are included on every plan, and sandboxes for systems such as Workday are on Enterprise (pricing).
How secure is Apideck?
Apideck holds SOC 2 Type II and self-certifies GDPR readiness (certifications). ISO 27001 is not among its listed certifications, and Apideck hosts in the EU only (Apideck).
Watch out
Ten ATS integrations and a three-resource model, with stage updates on one connector, leave out iCIMS, Oracle and most of the write paths recruiting products need. Pricing is per active consumer, so cost grows with the number of connected customers rather than API volume.
Which customers use Apideck for ATS integrations?
Apideck does not name ATS customers on its customer page.
5. Knit
Who is Knit best for?
Knit is best for products that want a stateless, webhook-push architecture, normalized EEOC data, and ATS alongside many other categories.
Which ATS systems does Knit cover?
Knit lists 40 ATS integrations in its ATS apps catalog as of October 13, 2026, including Workday, SAP SuccessFactors, Oracle Cloud HCM, Oracle Taleo, iCIMS, UKG Pro Recruiting, Bullhorn, Greenhouse, Lever, Ashby, Workable, SmartRecruiters, Jobvite, Breezy, JazzHR, Pinpoint, Recruitee, Teamtailor, Zoho Recruit and Personio. Knit’s Greenhouse connector authenticates against Harvest v3 (Greenhouse guide), but Knit does not publish its Greenhouse partner status.
How deep is Knit’s ATS data model?
Knit documents creating applications with a candidate, attachment and source, updating application stage, rejecting with a rejection reason and a note, adding attachments to applications, reading notes and creating candidate notes, tags, rejection reasons and EEOC records. Interviews and offers are nested in applications, and scorecards are not in the model. Each endpoint page lists the apps it supports: stage updates cover 24 ATS (update stage) and rejections 14 (reject application), though the rejection reason is ignored on 3 of them and the note on 2.
How does Knit sync ATS data, and what does that mean for API traffic?
Knit forwards native webhooks and emits virtual webhooks by polling the ATS. Where the ATS has no webhooks, freshness depends on Knit’s sync frequency, which is 24 hours on the Start Up plan and configurable on higher plans (pricing), down to every five minutes (sync frequency). Your application owns ingestion, ordering, and idempotency of the pushed events.
Can Knit map and transform custom fields?
Knit’s pricing lists custom field mapping on the Scale Up and Enterprise plans, but its field-mapping API is in beta and documents employee and CRM records only, not ATS objects (add custom field mapping). For ATS custom fields, plan on the passthrough API, available on every plan (pricing). There is no documented transform layer.
How good is Knit’s developer experience and support?
Knit ships a Python SDK (Knit unified API), a Postman collection, a connect component with guides for React, Vanilla JS, Angular and Vue, and an AI Connector Builder. Log retention is 3 days on Start Up, 30 days on Scale Up and 90 days on Enterprise. Support is by email on Start Up and by Slack or email on Scale Up (pricing).
How secure is Knit?
Knit holds SOC 2 Type II and ISO 27001 and is GDPR compliant (security). HIPAA is not listed on its security page or FAQ. Knit processes data in the US, EU or India, and multiple data-center locations and single-tenant hosting are on the Enterprise plan.
Watch out
Interviews and offers are read-only inside the application object, and scorecards are not in the unified model. On ATS without native webhooks, changes arrive on Knit’s sync schedule, which is daily on the Start Up plan.
Which customers use Knit for ATS integrations?
Wayfaster
6. Ampersand
Who is Ampersand best for?
Ampersand is best for teams whose integrations center on CRM and go-to-market systems such as Salesforce and HubSpot, that need Ashby or Lever alongside them, and that want to define integration logic as code. It is a code-first integration platform, not a unified ATS API, so it sits closer to Nango than to the other providers here.
Which ATS systems does Ampersand cover?
Ampersand’s documentation lists Ashby, Breezy and Lever under HR and recruiting, and Loxo among vertical CRMs. Workday is available as an auth and proxy connector only, and the documentation has no connector for Greenhouse, iCIMS, SAP SuccessFactors or Oracle (Ampersand provider guides). Ampersand’s own ATS comparison, published June 15, 2026, names Greenhouse as supported, which its documentation did not reflect on October 13, 2026.
How deep is Ampersand’s ATS data model?
Ampersand works with each ATS’s native objects rather than a unified model. On Ashby it reads and writes applications, candidates, jobs, offers and interview schedules, and reads application feedback, interviews and archive reasons (Ashby guide). On Lever it reads opportunities, postings, stages, archive reasons and sources, but its write actions do not include opportunities, so stage changes and archiving go through proxy calls to Lever’s API (Lever guide).
How does Ampersand sync ATS data, and what does that mean for API traffic?
Ampersand runs scheduled read actions defined in an amp.yaml manifest, as often as every 10 minutes (read actions), and delivers the results to a destination such as your webhook endpoint or a queue. On Ashby, incremental reads cover applications, application feedback and interview schedules only. Every other object is re-read in full on each scheduled read, so traffic grows with the size of the customer’s Ashby instance. Subscribe Actions, Ampersand’s near-instant webhooks, are supported for a subset of providers, and the Ashby and Lever guides do not list them. Subscribe Actions also produce no operations or logs in the Ampersand dashboard (Subscribe actions).
Can Ampersand map and transform custom fields?
Yes, per customer. Via SDK, each of your customers maps their fields inside your product. Value mapping is one-to-one, and there is no general transform logic (field mapping).
How good is Ampersand’s developer experience and support?
Integrations are amp.yaml manifests deployed with a CLI and CI/CD, with separate dev and prod projects and an AI SDK. Results can be routed to webhooks, S3, SQS, Kinesis, Pub/Sub and data warehouses. There is no separate sandbox. Support is a shared Discord with Ampersand engineers on the startup program and a dedicated Slack channel on Growth (pricing).
How secure is Ampersand?
Ampersand’s trust center lists SOC 2 Type II, ISO 27001, HIPAA, GDPR and CCPA. EU data residency and on-prem deployments are available on its enterprise tier (Ampersand).
Watch out
Recruiting is a small part of a catalog built around CRM and go-to-market systems, so enterprise ATS coverage and per-ATS logic stay with your team.
Which customers use Ampersand for ATS integrations?
Ampersand does not name ATS customers on its customer page.
7. Nango
Who is Nango best for?
Nango is best for teams that treat integrations as a core part of their product and have the engineering bandwidth to build ATS models, syncs and write paths on top of Nango’s infrastructure.
Which ATS systems does Nango cover?
Nango supports 1,000+ APIs across 30 categories, and its catalog tags 25 systems as ATS as of October 13, 2026, including Greenhouse, Lever, Ashby, Workable, SmartRecruiters, Bullhorn and Teamtailor (Nango API catalog).
How deep is Nango’s ATS data model?
User-defined. You define the models and maintain every write path (Nango unified APIs). Nango offers pre-built syncs and actions for some ATS, such as Workable (24 syncs) and Lever (17 syncs), while others such as Jobvite and JazzHR have none yet. On Ashby, Lever and Workable these include actions to create candidates, change stages and add notes, each returning that ATS’s own data shape for you to copy and maintain.
How does Nango sync ATS data, and what does that mean for API traffic?
You define each sync, its schedule and its webhook handling in code, so the API footprint is whatever you design.
Can Nango map and transform custom fields?
Build it yourself, per ATS, in your own repository.
How good is Nango’s developer experience and support?
Request and response logs kept for 15 days, OpenTelemetry export, an open-source core, free self-hosting of auth and proxy with full self-hosting on Enterprise, and setup guides for AI coding agents such as Claude Code and Cursor (observability). Support is in-app chat on the free and pay-as-you-go plans and a private Slack Connect channel on the Growth add-on and Enterprise (pricing).
How secure is Nango?
Nango is SOC 2 Type II certified, GDPR compliant and HIPAA compliant (security).
Watch out
Workday Recruiting and SuccessFactors edge cases surface over months of production traffic, along with the partner agreements, rate-limit handling and per-customer stage configurations that come with them. AI coding agents shorten the first build, but they don’t shorten that tail.
Which customers use Nango for ATS integrations?
Nango does not name ATS customers on its customer page.
Which adjacent providers come up in ATS integration evaluations?
JobSync, Truto, embedded iPaaS tools and Finch come up in ATS integration evaluations, but none is a direct alternative to a unified ATS API for recruiting tech.
- JobSync: JobSync manages apply flows and job distribution into enterprise ATS such as Workday, SuccessFactors, Oracle and iCIMS, deduplicating applicants and maintaining ATS validation rules (JobSync). It serves job boards and talent-attraction tools that need candidates delivered into the ATS, rather than products that read and write recruiting data across a normalized model.
- Truto: Truto is pass-through by default, with an optional scheduled sync through RapidBridge (Truto pricing). Truto positions itself as complementary to Kombo to cover adjacent integration categories rather than as a direct alternative. They’re for instance a great option for extending coverage across accounting or security systems.
- Embedded iPaaS (Workato Embedded, Paragon): These tools orchestrate customer-facing workflows. They do not normalize Greenhouse, Workday Recruiting and iCIMS into one model, so the ATS modeling work stays with you.
- Finch: Finch is a unified API for HRIS and payroll covering 250+ systems (Finch). Finch announced an ATS API beta in October 2022, but its current developer documentation has no ATS API (Finch docs).
How do the providers compare on ATS sync architecture?
| Provider | Architecture | Default freshness | Native webhooks consumed / virtual webhooks | Scoped sync options | Deletion tracking | What API traffic scales with |
|---|---|---|---|---|---|---|
| Kombo | Native webhooks plus scheduled delta sync, with candidate package sync for full syncs on supported ATS | Native webhooks in real time, scheduled sync down to 5 minutes | Native consumed on 19 ATS, no polling-based virtual webhooks | Created applications only (default), sync all, optionally limited by cutoff date or rolling window | Yes | Default mode: applications your product creates. Sync all: recently changed candidates, with older ones refreshed less often |
| Merge | Full scheduled sync, copy and store | Daily on Launch; customizable on Professional and Enterprise, down to 1 to 5 minutes on the highest setting | Native consumed on Professional and Enterprise; no virtual webhooks | Selective Sync time-based filters, coverage varies by integration | Yes, full-coverage detection is a paid add-on | Size of the customer's ATS |
| Unified.to | Live pass-through | Live on read | Native passed through, virtual webhooks by polling, down to 1 minute | Not applicable | Where the integration supports it | Your reads and polling interval, instance size on every full read |
| Apideck | Live pass-through | Live on read | Virtual webhooks by polling, typically every 24 hours | Not applicable | No | Your reads and polling interval |
| Ampersand | Scheduled reads defined in amp.yaml, delivered to your destination | Read schedule you set, as often as every 10 minutes | Subscribe Actions for a subset of providers, not listed for Ashby or Lever | Objects and fields you define | Not documented for ATS | Read schedule |
| Knit | Pass-through, webhook push | Native webhooks forwarded; polling every 24 hours on Start Up, configurable down to 5 minutes | Native forwarded; virtual webhooks by polling | Native ATS filters, per Knit's filter support matrix | Per integration | Polling cadence and reads |
| Nango | Defined by you | Defined by you | Build it yourself | Build it yourself | Build it yourself | Whatever you design |
How do the providers compare on ATS data coverage?
| Operation | Kombo | Merge | Unified.to | Apideck | Ampersand | Knit | Nango |
|---|---|---|---|---|---|---|---|
| Jobs, candidates and applications read | Full | Full | Full | Partial | Partial, Ashby and Lever; Breezy jobs only | Full | Template: Ashby, Lever, Workable, Greenhouse (basic) |
| Create candidate / application | Full, applications on 103 | Partial, candidates 34, applications 24 | Partial, candidates 93, applications 63 | Partial | Partial, Ashby | Full, applications on 35 | Template: Ashby, Lever, Workable |
| Attachments | Partial, upload on 57 | Partial, upload on 18 | Partial, documents write on 44 | Minimal, CV URL field on applicants | Workaround, proxy only | Partial, upload on 28 | Build it yourself |
| Move stage | Partial, 52 integrations | Partial, 17 integrations | Workaround, status-field write on 46; exact stage only where original_status is writable, otherwise an undocumented mapping from a normalized status | Minimal, Teamtailor only | Workaround, proxy only | Partial, 24 integrations | Template: Ashby, Lever, Workable |
| Rejection reasons and outcome read | 79 ATS | Partial, reject reasons on 16 | Partial, rejected reason on 33 | Minimal, application status | Partial, archive reasons on Ashby and Lever | Partial, reasons on 11 | Template: Lever, Workable |
| Reject with reason | Partial, with note on 24 | None for existing applications; reason on create on 3. Workaround: Agent Handler, a separate product | Workaround, rejected_reason field writable on 7; no reject operation | None | Workaround, proxy only | Partial, 14 integrations; reason ignored on 3, note on 2 | Template: Lever archive, Workable disqualify; reason not documented |
| Source read | Partial | Partial, 33 integrations | Partial, 95 integrations | Minimal, applicant sources | Partial, Ashby and Lever | Minimal, origin type | Template: Ashby, Lever |
| Automatic source attribution on create | Full | None, manual source field on create | None, manual source field | None, manual sources field | Not documented | None, manual source field on 9 | Build it yourself |
| Interviews | Partial, read on 17 | Partial, read 11, create 3 | Partial, read 38, write 12 | None | Partial, Ashby read and schedule write | Partial, read-only, nested in application | Template: Ashby, Lever, Workable |
| Scorecards | Partial, read only on 5, write coming soon | Partial, read-only on 7 | Partial, read 31, write 11 | None | Partial, Ashby application feedback read | None | Template: Lever feedback read, Workable ratings write |
| Notes read / write | Partial, read 9, write 44 | Partial, as activities: read 20, write 9 | Partial, as activities of type NOTE; activity write on 53 | None | Workaround, proxy only | Partial, read 14, create 23 | Template: write on Ashby, Lever, Workable; read on Lever |
| Offers | Partial, read on 12 | Partial, read on 14 | Partial, read-only, nested in application | None | Partial, Ashby read and write | Partial, read-only, nested in application | Template: read on Lever, Workable |
| Custom fields | Full: read on every plan, write through remote fields on create, TypeScript transforms on Enterprise | Full, mapping and JSONata on Professional and Enterprise | Partial, read and write via metadata; no per-customer mapping or transforms | Partial, select and rename on Scale and Enterprise | Partial, per-customer field and value mapping; no transforms | Minimal, field mapping in beta and not documented for ATS objects | Build it yourself, with full control in your code |
How to read this table: Full = documented on most integrations. Partial = documented on a subset, or per-system coverage not published. Minimal = narrow object or field set. None = not in the unified model. Not documented = not covered in the provider's docs. Template = pre-built code per ATS that you copy and maintain, each in that ATS's own data shape. Workaround = not a native operation: possible only through passthrough or proxy calls, a generic field write with no documented mapping to the customer's own stages or reasons, or a separate product. Build it yourself = no pre-built model. All other statuses are native operations in the provider's model that target the customer's own configuration, such as their stages and rejection reasons. Every provider also offers passthrough to the ATS's own API (Merge on Professional and Enterprise), so the table names passthrough only where it is the only route.
- Unified.to changes stages by writing the application's status fields. It can target the customer's exact stage only where
original_statusis writable; elsewhere a normalized status is mapped to the customer's stages in a way Unified.to doesn't document. - Merge has no endpoint to reject an existing application. A reason can be set when creating an application on 3 integrations, and Merge's separate Agent Handler product can reject on some systems.
- Unified.to has no reject operation; the
rejected_reasonfield is writable on 7 integrations. - Knit ignores the rejection reason on 3 of the 14 integrations and the note on 2.
- Manual field: you can set a source value yourself when creating an application, but the provider doesn't attribute applications automatically.
- Nango templates: reads on Ashby, Lever, Workable and basic Greenhouse syncs; reject through Lever archive and Workable disqualify, with passing a reason not documented; scorecards as Lever feedback read and Workable ratings write; notes written on Ashby, Lever and Workable and read on Lever.
- Nested: returned read-only inside the application object.
- Merge and Unified.to model notes as activities. Unified.to's count is for activity writes.
- Kombo reads custom fields on every plan, writes extra data through remote fields when creating candidates and applications, and transforms values with TypeScript formulas on Enterprise.
- Plan limits: Merge field mapping and JSONata on Professional and Enterprise; Apideck field mapping on Scale and Enterprise.
Counts are the integrations each provider's own docs list for the operation on October 13, 2026, with duplicate listings of the same system counted once.
How do the providers compare on enterprise ATS support?
| ATS | Kombo | Merge | Unified.to | Apideck | Ampersand | Knit | Nango |
|---|---|---|---|---|---|---|---|
| Workday Recruiting | Certified partner | Certified partner | Supported | Supported | Connectivity only, auth and proxy | Supported | Connectivity only |
| SAP SuccessFactors Recruiting | Certified partner | Supported | Supported | Supported | Not listed | Supported | Not listed |
| Oracle Recruiting Cloud | Certified partner | Supported | Supported, as Oracle HCM | Not listed | Not listed | Supported, as Oracle Cloud HCM | Not listed |
| Oracle Taleo | Supported | Supported | Not listed | Not listed | Not listed | Supported | Not listed |
| Greenhouse (Harvest v3) | Certified partner | Supported, v3 partner status not published | Supported, v3 partner status not published | Supported, v3 partner status not published | Not listed | Supported, v3 partner status not published | Template: basic syncs; you sign the Harvest v3 partnership yourself |
| iCIMS | Supported | Supported | Supported | Not listed | Not listed | Supported | Not listed |
| UKG Pro Recruiting | Certified partner | Supported | Supported | Not listed | Not listed | Supported | Not listed |
| SmartRecruiters | Supported | Supported | Supported | Not listed | Not listed | Supported | Connectivity only |
| Lever | Supported | Supported | Supported | Supported | Supported | Supported | Template |
| Ashby | Supported | Supported | Supported | Not listed | Supported | Supported | Template |
| Avature | Supported | Not listed | Supported | Not listed | Not listed | Not listed | Not listed |
| Phenom | Supported | Not listed | Supported | Not listed | Not listed | Not listed | Not listed |
| Eightfold | Supported | Not listed | Supported | Not listed | Not listed | Not listed | Not listed |
| Cornerstone | Supported | Supported | Supported | Not listed | Not listed | Not listed | Not listed |
| Bullhorn | Supported | Supported | Supported | Supported | Not listed | Supported | Connectivity only |
How to read this table: Certified partner = the provider holds a published partnership with the ATS vendor. Supported = the provider ships the integration. Connectivity only = auth and pass-through; you build the integration. Template = pre-built syncs for that ATS that you copy and maintain. Not listed = not in the provider's ATS catalog on October 13, 2026.
- The provider lists Greenhouse but doesn't publicly state whether it holds a Harvest v3 partnership. Harvest v1 and v2 were retired on August 31, 2026, and v3 requires a signed Greenhouse partnership.
- Nango offers basic Greenhouse syncs; you sign the Harvest v3 partnership yourself.
Taken from each provider's public website and documentation on October 13, 2026.
How do the providers compare on field mapping?
| Provider | Select fields | Rename fields | Transform logic | Per-customer mapping | Configured in |
|---|---|---|---|---|---|
| Kombo | Yes | Yes | Yes, via TypeScript formulas on Enterprise | Yes | Dashboard |
| Merge | Yes | Yes | Yes, via JSONata | Yes | Dashboard |
| Unified.to | Yes, via metadata fields | Not documented | Not documented | Not documented | Metadata API |
| Apideck | Yes | Yes | No | Yes, by your customer in Vault | Vault UI |
| Ampersand | Yes | Yes | No, one-to-one value mapping | Yes | Via SDK |
| Knit | Beta, not documented for ATS objects | Beta, not documented for ATS objects | No | Beta, not documented for ATS objects | Field-mapping API (beta) |
| Nango | Build it yourself | Build it yourself | Build it yourself | Build it yourself | Your own codebase |
How to read this table: Yes = documented and available. Beta = in beta and not documented for ATS objects. No = not offered. Not documented = no public documentation found. Build it yourself = you implement it in your own code. Configured in = where mapping is set up; descriptive, not rated.
- Kombo: TypeScript formulas set per integration in the dashboard; transforms are on the Enterprise plan.
- Plan limits: Merge field mapping on Professional and Enterprise; Apideck field mapping on Scale and Enterprise.
Taken from each provider's public documentation and pricing pages on October 13, 2026.
Which ATS integration platform fits your use case?
The right unified ATS API depends on what your product writes back, which applicant tracking systems your customers run, and how much of their API allowance your integration can use. Most use cases have more than one reasonable choice, so each entry names our pick and when another provider fits better.
AI interviewing and screening: Kombo, or Unified.to for smaller instances. These products create applications, write results, move stages and reject with reasons. Kombo supports stage moves on 52 ATS, result links on 47 and reject-with-note on 24 as of October 13, 2026, and its default sync covers only the candidates you created. Unified.to writes stages through its status fields on 46 integrations, without documented mapping to the customer’s own stages, and suits products whose customers run small and mid-sized ATS. Merge writes stages on 17 integrations and has no reject endpoint, so it fits products that mostly read. See Kombo for AI screening.
Assessment and background checks: Kombo or Unified.to. Workday, SAP SuccessFactors, Oracle Recruiting Cloud, iCIMS, Greenhouse, and Lever have their own assessment modules, where recruiters order a test inside the ATS and expect the score back on the candidate. Kombo’s assessment API connects to these modules on 18 ATS as of October 13, 2026, so you receive the order and send back status, score, and a result link through one integration (assessment connectors). On ATS without a module, the ATS API covers the same flow, with result links on 47 ATS and stage moves on 52. Unified.to also offers an assessment API, so compare its per-ATS coverage. See Kombo for assessment.
Sourcing and attribution: Kombo or Unified.to. Application attribution tags the applications you create with your source, and a unified outcome per application shows which of your candidates were hired. If you only need to read where candidates came from, Merge (33 integrations) and Unified.to (95) both return a source field. See Kombo for recruiting and sourcing.
Hiring fraud detection: Kombo. Identity verification, deepfake detection and proxy-interview checks typically run on new applicants, so upstream filtering with a rolling window gives you recent candidates on Greenhouse, Workday and iCIMS without syncing years of history. Merge’s Selective Sync time filters narrow a full sync in a similar way where the ATS supports them, and Unified.to’s virtual webhooks can watch for new applications on smaller instances without storing candidate data. Among the three, Kombo has the most established presence in this space, working with leading providers such as Socure, Hiretofu, and Endorsed. We couldn’t find similar
Job boards and staffing: Kombo, or JobSync for apply flows. Kombo creates applications on 103 of its 108 ATS integrations, with screening-question answers on 56, and tracks outcomes for submitted candidates, including Bullhorn for staffing. Merge creates applications on 24 integrations. JobSync fits if you need a managed apply experience into enterprise ATS. See Kombo for job boards.
No API access to the ATS: Kombo’s AI Apply. When the customer can’t get you credentials, or the ATS has no API, AI Apply parses the job and submits the application through the browser. If you also need hiring outcomes, add the ATS API once the keys arrive. See Kombo AI Apply.
Talent analytics that need full history: Merge or Kombo. Pipeline analytics and talent rediscovery need the whole ATS. Kombo’s sync-all mode or Merge’s default sync is the right fit here. Expect API traffic to scale with the customer’s ATS, and agree on sync windows with enterprise customers on Workday and SuccessFactors. If you’d rather keep the copy in your own database, Unified.to’s Database Sync writes records there.
Several unrelated categories from one vendor: Merge or Unified.to. Merge covers ATS alongside CRM, accounting and ticketing with mature mapping, and hosts in the US, EU and APAC with a single-tenant option. Unified.to covers more categories still and stores no data at rest, with the trade-offs on large instances described above.
Zero data at rest: Unified.to or Knit. Both store no candidate data. Check stage-update support per integration and plan for polling traffic on systems without webhooks. On an ATS with millions of candidates, ask each how long a full read takes and where that data lives afterwards.
Building it yourself: Nango. Nango gives you auth, sync infrastructure and observability. You own every ATS model, write path and partner agreement, including Greenhouse Harvest v3.
CRM-first stack with Ashby or Lever on the side: Ampersand. If most of your integrations are Salesforce and HubSpot and recruiting is a smaller need, Ampersand’s code-first model covers both. Check Lever’s write list and Ashby’s read schedule before you commit.
How should an AI recruitment platform integrate with its customers’ ATS?
Through a unified ATS API that picks up new applicants and stage changes quickly and writes results back into the ATS, because recruiters won’t switch tools to read them. Here’s how the four leading providers in this segment compare:
| Requirement | Kombo | Merge | Unified.to | Ampersand |
|---|---|---|---|---|
| Status changes | Native webhooks plus scheduled delta sync | Scheduled sync, native webhooks on Professional and Enterprise | Native webhooks passed through, otherwise polling-based virtual webhooks | Scheduled reads, Subscribe Actions not documented for ATS connectors |
| Stage moves | 52 ATS | 17 ATS | Not native: status-field write on 46 ATS, without documented mapping to the customer's own stages | Not native: proxy calls on Ashby and Lever |
| Reject with reason | 24 ATS, with note | No reject endpoint | Not native: rejected_reason field writable on 7 ATS, no reject operation | Not native: proxy calls |
| Enterprise coverage (Workday, SuccessFactors, iCIMS, Oracle, Bullhorn) | Listed | Listed | Listed | Workday auth and proxy only; others not listed |
How to read this table: Native = a dedicated operation in the provider's model that targets the customer's own stages and rejection reasons. Workaround = not a native operation: possible only through passthrough or proxy calls, or a generic field write with no documented mapping to the customer's own stages or reasons. None = not available. Listed = all five systems are in the provider's ATS catalog. Not listed = not in the provider's ATS catalog. Status changes row = how changes reach your product; descriptive, not rated.
- Unified.to changes stages by writing the application's status fields. It can target the customer's exact stage only where
original_statusis writable; elsewhere a normalized status is mapped to the customer's stages in a way Unified.to doesn't document. - Unified.to has no reject operation; the
rejected_reasonfield is writable on 7 integrations.
Counts from each provider's own docs on October 13, 2026, with duplicate listings of the same system counted once.
To summarize, Kombo is the strongest fit for products selling into mid-market and enterprise customers. Unified.to fits products that want the broadest catalog and zero data at rest, and can work with status-field stage updates, without documented stage mapping, on a subset of integrations. Merge fits when ATS is one of several categories you need from one vendor. Code-first platforms such as Nango and Ampersand fit teams that want to own the integration logic and feel confident building ATS depth themselves.
What can you do when you can’t get API access to the ATS?
For many job boards and programmatic agencies, most job inventory sits behind ATS they can’t integrate with. Enterprise employers take months to approve API access, jobs that arrive through XML feeds come without a direct employer relationship, and some career sites have no API at all. Those jobs end in a redirect to the employer’s ATS, where up to 90% of interested candidates never finish the application (Kombo AI Apply).
Kombo’s new AI Apply product lets them offer easy apply on those jobs anyway. A browser agent reads the application form from the job posting URL, including screening questions, and returns it as JSON, so the form runs natively in your product. When the candidate submits, Kombo files the application on the employer’s career site and reports the result by webhook (AI Apply docs). Because Kombo submits the application itself, attribution no longer depends on the candidate accepting tracking cookies.
Recruitics, StepStone, CV-Library, College Recruiter, Bandana and Placed are among the job boards and programmatic agencies using AI Apply. Across hundreds of thousands of submitted applications, customers report 3 to 5 times more completed applications, near-100% attribution and a 99.9% delivery success rate (Kombo). Onboarding a new employer takes under two hours (AI Apply).
AI Apply complements the ATS API rather than replacing it. It confirms delivery and attribution, but interview, hire, and rejection outcomes still come from the API, so many teams use the API where they have credentials and AI Apply for everything else.
How to run the evaluation yourself
Whatever this page concludes, put these questions to every ATS integration provider you talk to, and ask for evidence rather than answers.
- How many API calls does your integration make per day against a Workday or Greenhouse tenant with 200,000 candidates? Can I see the logs?
- Can you sync only the candidates my product created or touched?
- Which ATSs do you consume native webhooks from, and what runs underneath them?
- Are you an approved Greenhouse Harvest v3 partner?
- On the systems I need, can I move applications to my customer’s own stages and reject with their own reasons through a native operation, not passthrough or a generic status field? Show me the per-system list.
- Do applications return rejection reason, outcome and source?
- Who handles SuccessFactors 429s, and do real-time writes wait behind a running sync?
- Can I transform a custom field, or only select it, and can my support team change a mapping without a release?
- Do you have a sandbox for Workday Recruiting and SuccessFactors, and can I have access this week?
- If my customer can’t get API credentials, or the ATS has no API, what can I still do, and what does that not cover?
Frequently asked questions
What are the best unified APIs for ATS integrations?
The leading unified APIs for ATS integrations in 2026 are Kombo, Merge, Unified.to, Apideck, Knit, Ampersand and Nango. Kombo offers scoped candidate sync and the broadest documented write coverage for stage moves and rejections, Merge offers ATS alongside many other categories, and Unified.to offers the largest catalog with zero data at rest. The right choice depends on which applicant tracking systems your customers use and what your product writes back.
What is the best middleware for integrating with my customers’ ATS?
For customer-facing ATS integrations, a unified ATS API is usually a better fit than general-purpose middleware or embedded iPaaS. Workato Embedded and Paragon orchestrate workflows but leave you to model each ATS’s stages, dispositions and custom fields yourself. A unified API such as Kombo or Merge normalizes Greenhouse, Workday Recruiting, iCIMS and others into one data model and maintains the partner access.
Which unified ATS APIs support Greenhouse Harvest v3?
Greenhouse Harvest v1 and v2 were removed on August 31, 2026, and Harvest v3 requires a signed Greenhouse partnership agreement for partner integrations. Kombo is a certified Greenhouse partner (Greenhouse Partner Directory). Its Greenhouse (V3) connector supports Harvest v3 on your own Greenhouse partner credentials, and Kombo refers you into Greenhouse’s partner program. Merge, Unified.to, Apideck and Knit list Greenhouse but do not state their v3 partner status publicly, so ask each vendor directly.
Which unified ATS APIs support Workday Recruiting and Oracle Recruiting?
Kombo, Merge and Unified.to list Workday and Oracle’s recruiting product in their ATS catalogs (Unified.to as Oracle HCM), and Kombo and Unified.to also list Avature, Phenom and Eightfold. Kombo holds certified partnerships with Workday and Oracle, and Merge is a Workday partner. Knit lists Workday and Oracle Cloud HCM, and Apideck lists Workday but not Oracle.
How can an assessment platform sync candidates and send scores back to the ATS?
Through the ATS’s own assessment module where one exists. The recruiter orders an assessment inside Workday, SAP SuccessFactors, iCIMS, Greenhouse or another ATS, your product receives the candidate and job, and the score lands back on the candidate’s profile. Kombo’s assessment API covers these modules on 18 ATS with one integration. Where the ATS has no assessment module, a unified ATS API can create the candidate, post a result link and move the stage instead.
How do you integrate with an ATS when you can’t get API access?
It depends on why. If the ATS has an API but access is gated by a partnership, a security review or paid credentials, a unified ATS API that already holds the partnership gets you in. If the credentials are out of reach or the ATS has no API, a browser agent integration works through the public interface instead. Kombo’s AI Apply does this for reading jobs and submitting applications: you send a job URL, get the application form back as JSON, and Kombo submits the candidate’s answers. It returns delivery and attribution but not hiring outcomes, so teams that need those switch to the ATS API once credentials arrive.
Do ATS vendors charge for API usage?
Some now meter, gate or throttle it. Workday meters production API calls above an annual allowance from February 1, 2027, SAP throttles SuccessFactors tenants at 600 requests per minute, and Greenhouse requires a partnership agreement for Harvest v3 access.
Is real-time pass-through or synced data better for ATS integrations?
For enterprise ATS, webhooks with a scheduled delta sync underneath is the better default. Live pass-through turns upstream rate limits into your rate limits, counts every read and poll against the customer’s API allowance, and has no deletion tracking. Pass-through suits low-volume, single-record lookups and buyers that require zero data at rest. For heavy read volume, Unified.to itself offers Database Sync, which writes records into your own database.
Should we build ATS integrations in-house or use a unified API?
Building Greenhouse, SAP SuccessFactors, Workday and iCIMS in-house means signing partner agreements, handling 429s and metering, and maintaining stage and disposition mappings per customer. Teams with dedicated integration engineers can do this with a code-first platform such as Nango. Most recruiting-tech teams buy a unified ATS API such as Kombo to ship those four systems without that team.
What are the best Merge alternatives for ATS integrations?
The main Merge alternatives for ATS integrations are Kombo, Unified.to, Knit, Apideck and Nango. Kombo is the closest alternative for teams that need deep ATS write coverage and a smaller API footprint, because it syncs only the candidates your product created by default. Unified.to and Knit suit teams that want zero data at rest. Between June and early October 2026, Merge’s changelog added one ATS integration and no new ATS write endpoints, while Agent Handler and Merge Gateway appeared in nearly every weekly entry (changelog).
How does Kombo compare to Merge for ATS?
Kombo lists 108 ATS integrations and Merge lists 63. As of October 13, 2026, Kombo supported stage moves on 52 ATS integrations against Merge’s 17, and reject-with-note on 24, while Merge has no endpoint to reject an existing application. Kombo syncs only created candidates by default, while Merge syncs the full ATS. Choose Merge if you need ATS plus unrelated categories from one vendor.
How does Kombo compare to Ampersand for ATS?
Ampersand is a code-first integration platform built around CRM and go-to-market systems. Its documentation lists Ashby, Breezy and Lever under HR and recruiting and Loxo among vertical CRMs, with Workday as auth and proxy only, and no unified ATS model. Kombo lists 108 ATS integrations, including Workday, SAP SuccessFactors, iCIMS and Greenhouse (V3), with one unified model plus raw remote data and passthrough requests. Kombo consumes native ATS webhooks where the ATS emits them and runs a scheduled delta sync underneath, while Ampersand’s documentation does not list Subscribe Actions for its ATS connectors.
How does Kombo compare to Unified.to and Apideck for ATS?
Kombo is the better option for connecting mid-market and enterprise end customers, while Unified.to and Apideck can be good options for connecting smaller end customers. Unified.to and Apideck read live from the ATS on every call and detect changes by polling, so every full read of a large instance runs through the ATS’s rate limits again, at 100 records per page on Unified.to. Kombo consumes native webhooks, runs a scheduled delta sync and stores only the candidates your product created by default. Unified.to supports stage updates through its application status fields on 46 integrations, without documented mapping to the customer’s own stages, and Apideck lists 10 ATS integrations with stage updates on one. Kombo lists 108 ATS integrations with stage moves on 52.
Does Finch support ATS integrations?
Finch is a unified API for HRIS and payroll, and its current developer documentation has no ATS API. For ATS integrations, compare Kombo, Merge, Unified.to and Knit.
Why isn’t JobSync in the comparison?
JobSync manages apply flows and job distribution into enterprise ATS such as Workday, SuccessFactors, Oracle and iCIMS. It is not a general read-and-write recruiting API for your product, so we list it among adjacent providers. Job boards that need a managed apply experience should evaluate JobSync alongside a unified ATS API.
Is Kombo only for European companies?
No. Kombo operates offices in New York and Berlin, runs isolated US and Canadian data regions, and holds certified partnerships with Workday, SAP SuccessFactors, Oracle, Greenhouse and UKG. Kombo provides support across West Coast, East Coast and European time zones on every plan, and covers US enterprise ATS including Workday, iCIMS, Oracle Recruiting Cloud, SmartRecruiters and Greenhouse.
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