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Version: 4.x

Changelog

Versioning Policy​

Socket.IO releases closely follow Semantic Versioning.

That means that with a version number x.y.z:

  • when releasing critical bug fixes, we make a patch release by increasing the z number (ex: 1.2.3 to 1.2.4).
  • when releasing new features or non-critical fixes, we make a minor release by increasing the y number (ex: 1.2.3 to 1.3.0).
  • when releasing breaking changes, we make a major release by increasing the x number (ex: 1.2.3 to 2.0.0).

Breaking changes​

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
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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