Socket.IO releases closely follow Semantic Versioning.
That means that with a version number
- when releasing critical bug fixes, we make a patch release by increasing the
- when releasing new features or non-critical fixes, we make a minor release by increasing the
- when releasing breaking changes, we make a major release by increasing the
Breaking changes are inconvenient for everyone, so we try to minimize the number of major releases.
We have had two major breaking changes impacting the Socket.IO protocol over the years:
- Socket.IO v2 was released in May 2017
- Socket.IO v3 was released in November 2020
Socket.IO v4 (released in March 2021) did not include any update to the Socket.IO protocol (only a couple of breaking changes in the Node.js server API), so it isn't counted here.
Reference: Migrating from 3.x to 4.0