Userscripts, often called Greasemonkey scripts, are a form of augmented browsing.
What I may write will probably be here.
Userscripts are available through many browsers with the installation of an addon known as a userscript manager. Often there are several to choose from. Greasemonkey was the first one, hence the moniker Greasemonkey scripts.
I do most of my browsing using Firefox and use the Violentmonkey userscript manager. I do minimal testing across different combinations of browsers and managers.
Any scripts I write can be found on Greasy Fork.
This is after the h1 but before API in the README.
There are multiple variations of the API documentation.