There are a bunch of useful userscripts for Stack Overflow out there. Userscripts add functionality to the site by running scripts in your browser. All major browsers support userscripts by installing a userscript manager extension, for example Tampermonkey or Violentmonkey.

Our own scripts

See our GitHub userscript repository with the full list of our scripts!
Our most commonly used scripts

Endorsed scripts

Additional Stack Exchange userscripts