Best unified APIs for HRIS, ATS, and payroll integrations in 2026

The guide compares six unified API platforms for SaaS products and AI agents that need connections to HRIS, applicant-tracking, and payroll systems, emphasizing challenges such as fragmented provider APIs, enterprise authentication, data freshness, sensitive employee information, and scoped agent permissions. It evaluates Nango, Merge, Finch, Kombo, Apideck, and Knit across provider coverage, read and write support, synchronization speed, customization, raw API access, deployment, pricing, and capabilities beyond HR. Nango is presented as the broadest and most flexible option, combining HR, ATS, payroll, agent tools, code-level customization, and integrations across more than 1,000 APIs, while Merge is positioned for teams seeking a vendor-maintained normalized data model, Finch for US payroll and benefits deduction write-backs, Kombo for European people-data and recruiting use cases, Apideck for accounting-focused products needing basic HR data, and Knit for managed HR integrations in India, APAC, and staffing. The guide advises buyers to test their most difficult integrations, such as Workday or ADP, and select a platform based on their geographic needs, required write operations, data-latency tolerance, AI-agent requirements, and control over sensitive employee data.

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