Bookmarklets (and Custom URL Schemes) Are Criminally Underrated

You Can Add Custom Buttons To Your Browser That Do Whatever "Bookmarklets" are an underutilized and frankly little-known feature in Chrome and Firefox (and probably most other browsers too) that allows you to create a bookmark that contains a little bit of JavaScript instead of a link to a web page. That doesn't seem too exciting, but combined with the ability to put bookmarks on a bookmark toolbar, we can create custom buttons that can take arbitrary action within the context of the currently-loaded page, including sending the URL or content from that page to another one, or even to an external program.