> ## Documentation Index
> Fetch the complete documentation index at: https://docs.slm.m1amdocs.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Versioning

## V2

This topic shows information relevant specifically for Subscribe REST API version 20210401 referred to as V2

The API version is based on the date of the last breaking change.

The current version is 20190501.

The current version is 20210401.

To set the API version on a specific request send an **X-API-Version** header on your first call. The system will default according to your first call.

Most additions to the API will not require a new version of the API.

If no version is specified in the X-API Version header, the default API version will be used.

**Parent topic:**[Subscribe REST API Overview](../topics/Overview)


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