DevLogin

Login with your own Minecraft account in a mod development environment.
This works on all Minecraft versions with any mod loader. (In case of Forge, only on versions supporting Mixins: 1.15.2+)

Usage

To use this mod, add

repositories {
  mavenCentral()
}

dependencies {
  modImplementation "com.ptsmods:devlogin:3.5" // For Fabric and Quilt
  implementation fg.deobf("com.ptsmods:devlogin:3.5") // For Forge
}

to your build.gradle file.

After that, the procedure differs for different account types. You have the following options:

1. Microsoft account
2. Mimicking

Microsoft account

If you have Migrated your Minecraft account to a Microsoft account, you can still use this mod just fine. The procedure is just a little more complicated.

1. Add either the --msa or --msa-nostore program argument to your run configuration and launch the configuration. Use --msa-nostore to prevent DevLogin from storing your refresh token which can be used indefinitely to get new Minecraft tokens.
2. In a moment, you should see a dialog asking you to fill in a code on a website. Follow these instructions.
3. The dialog should disappear and Minecraft should start a moment later, logged in on your Minecraft account. This dialog can be disabled, however, by passing the --msa-no-dialog program argument. In this case the code is printed to the console which may be desired if you have issues with the dialog.
4. That's it, if the Minecraft token expires, a new one will be obtained using the refresh token unless --msa-nostore was passed instead of --msa in which case you'll have to redo this procedure.

Mimicking

If you don't want your password or tokens stored anywhere potentially unsafe and don't mind not being able to log onto servers or just simply wish to pretend to be some famous YouTuber or Mojang employee or whatever, you can add the --mimicPlayer <PlayerName or UUID> program argument instead.
This yields more or less the same result, mimicking just doesn't actually log in, so you cannot join online servers.