HR software integrations explained: native, middleware, API and file
Updated 28 October 2026 · 5 min read
“Integrates with” on a vendor's website can mean anything from a one-click connection to a CSV file you upload every month. Knowing the difference before you buy saves a lot of manual work later.
The four kinds of connection
- Native: built and maintained by one of the vendors. Usually the most reliable; switch it on and map a few fields.
- Middleware or unified API: a third-party platform moves the data. Works well, but adds another subscription and another place things can break.
- Open API: the vendor offers an API and your developers build the connection. Flexible, but you own the build and its upkeep.
- File (CSV or SFTP): data is exported and imported on a schedule. Simple and common for payroll, but not real-time.
Which data should flow where
Core HR is the system of record. New hires flow in from recruiting; job, pay and personal changes flow out to payroll, time, learning and other tools; leave and attendance flow back into payroll. Draw this map for your own tools and mark which links are native.
What to ask vendors
- Is the connection to our HRIS native, through middleware, API or file?
- Which data moves, in which direction, and how often?
- Who fixes it when it breaks, and is it included in the price?
- Can we see the API documentation before we sign?
On hrstack every connection shows its type, its source and whether the vendor confirmed it, so you can see the weak links in a stack before you commit.
Frequently asked questions
What is a native integration?
A connection built and maintained by one of the two vendors, usually switched on in settings without custom development.
Is a CSV integration a real integration?
It moves data, but on a schedule and with someone running it. For payroll it is common and acceptable; for hiring or onboarding, a native connection saves more time.