This is the Fabric version of OAuth. For Forge look here!

This mod adds a way to auth within your game in the multiplayer screen. After, it will ask the login type. If you select Microsoft it'll open in your default browser so you can securely login. Otherwise click Mojang login to login with your username/email just like you would in the normal Minecraft launcher. If you leave the password field blank you can login offline with any username you want! This only works on offline servers or in singleplayer however.

Features:

Supports Legacy, Mojang, and Microsoft account logins.
Adds a new button to the multiplayer screen to login and fix invalid sessions.
Allows you to login to different accounts without closing your game.
Ability to set your username for playing offline by leaving the password field blank.
Mod only needs to be installed on the client to work.