Fastify, the fast and low overhead web framework for Node.js, has recently shipped Fastify v5. In order to support Fastify v5 a new major version of @clerk/fastify had to be released. With Clerk's Fastify SDK 2.0 comes full support for Fastify v5 and no breaking changes for the Clerk SDK itself.

If you're using Fastify and @clerk/fastify, you can update like so:

1. Follow the official Fastify v5 migration guide
2. Install the latest version of @clerk/fastify

3. You're done! No further changes needed

@clerk/fastify@^2.0.0 only supports Fastify v5 or later, if you want/need to continue using Fastify v4, please stick with @clerk/fastify@^1.0.0.