Violentmonkey

Violentmonkey is an open-source userscript manager created by Gerald Liu in 2013 under the MIT license. It provides userscript execution for web browsers following the WebExtensions standard. Operating as a lightweight alternative to closed-source script managers, it runs entirely inside the local browser environment without transmitting tracking analytics or injecting third-party telemetry. It allows users to execute custom scripts on designated web domains to automate workflows and adjust page interfaces.

Text from OyList