Versioning {#uc_versioning}
===========================

`Unified Checkout` uses [Semantic Versioning](http://semver.org/spec/v2.0.0.md "") (SemVer). Version numbers use the `MAJOR.MINOR.PATCH` format:

* **MAJOR**: breaking changes that require code modifications
* **MINOR**: new features that are backwards compatible
* **PATCH**: bug fixes and improvements that are backwards compatible  
  The server controls which SDK version is loaded for each session that you request. When your server creates a session, the response JWT includes a clientLibrary field that contains the full URL to the correct version of the SDK. Your server parses the JWT, extracts the URL, and passes it to the frontend to load dynamically.

> IMPORTANT
> The ` clientVersion ` field in the session request is optional. When you do not include this field, the server automatically resolves the appropriate version for every session. This ensures that the client-side library and server-side features are compatible.` Cybersource ` recommends that you do not include the ` clientVersion ` field in your request and that you use the most recent version. When you do this, your integration benefits from new features, payment methods, and improvements and there are no code changes required.

Pin to a Version
----------------

If you must set your integration to a specific version, you can set the `clientVersion` field to a `MAJOR` version such as `1`, or a `MAJOR.MINOR` version such as `1.2`. The server uses the latest compatible patch release within that range. This ensures that you continue to receive security fixes and bug fixes.

> IMPORTANT
> You cannot pin to a specific patch version (` MAJOR.MINOR.PATCH `). This ensures that all integrations receive critical patches. ` Cybersource ` recommends omitting clientVersion from your request unless you have a specific need for pinned behavior.  
> For information about the latest releases, see [Client Version History](/docs/cybs/en-us/unified-checkout/developer/all/rest/unified-checkout/uc-getting-started-ss-setup/uc-capture-context-versions.md "").