Jetpack | 2009-2010
In early 2009, building a Firefox add-on was hard: multiple files using obscure formatting rules had to be written, and silently failed if a single unfortunate typo was made. Debugging information was scarce, and changing the behavior of the add-on required restarting all of Firefox.
Jetpack attempted to change this by making both the development cycle and the installation process restartless. Clean APIs with interactive tutorials embedded in their documentation allowed users to tinker with code and instantly see the results in their browser chrome.