Netscape Plugin Application Programming Interface (NPAPI) is an application programming interface (API) that allows plug-ins (more specifically, browser extensions) to be developed for web browsers. It was first developed for Netscape browsers, starting in 1995 with Netscape Navigator 2.0, but was subsequently adopted by other browsers.
I have looked for duplicate questions but cannot find one that is general enough to answer the question I have. I would like to know in what versions of different major browsers (Firefox, Chrome, etc.) NPAPI support was dropped, meaning from what version can these no longer be expected to work, and what version of a specific browser you need to run to make sure they do.
Running outdated software is never a good idea, and running an old browser should be an absolute last resort after doing research into the alternatives (such as Java Web Start), but please stick to the topic. The question is not what the pros and cons are, or an invitation to discuss why NPAPI support was dropped, or whether it's a good thing or not that it was.
The only question is: In what versions of major browsers was support for NPAPI plugins dropped?