This is the first maintenance release in the 3.1 stable branch released last March.

With the -stable releases we offer you the backwards compatible changes and bugfixes. However in this release we had to break some compatibility with networking due to a security issue. See the Known incompatibilities section of the blog post. If we inadvertently changed behavior for your project started with Godot 3.1-stable please report a bug.

Check the detailed release notes for Godot 3.1.1 on the Godot blog!