This brought back some memories. In July 2004, I made a Firefox extension to "fix" a bad redesign of the website All Music Guide (my blog post: http://www.holovaty.com/writing/all-music-guide/). To my knowledge this was the first instance of a site-specific browser extension.
Aaron Boodman saw that idea and took it much farther by developing Greasemonkey, which made the idea more general and more powerful.
No mention of Binary Behaviors (https://docs.microsoft.com/en-us/archive/msdn-magazine/2001/...), but I guess these could go in the ActiveX bucket. They are a bit more interesting than plug-ins when you consider where some of the current innovation is happening with front end web development and standards.
> One notable startup I’ve come across is Insight Browser, an iOS browser that allows users to build and share simple extensions.
I've worked with the Insight [1] folks (YC W19, I think?) to port my Chrome extension [2] to their platform. They made it super easy, and I'd recommend others give them a try. Not every extension makes sense on iOS, but for those that do, this can be a slick way to finally reach iOS users.
Hopefully Insight can popularize mobile extensions and generate some competition in the mobile browser space!
Aaron Boodman saw that idea and took it much farther by developing Greasemonkey, which made the idea more general and more powerful.