This left only Project64 as the only relevant and active emulator still using the zilmar spec. Mupen64 was forked into Mupen64Plus and developed its own plugin spec that was incompatible with the older zilmar spec, making it unable to use existing plugins unless they were specifically ported to it. 1964's development eventually ceased, and it completely fell off the radar. However, as time went on, things began to change, though slowly at first. Hence the label 'plugin hell' was coined, and stuck as a description of the travails of trying to emulate N64 games well into the 2010's. Unsurprisingly, this situation often led to a lot of confusion from users, who often wondered why there were so many plugins, and which ones were the best to use, only to find out it often depended on the game, and even then, some games would refuse to work as intended no matter what was tried. To illustrate the point, here is a site that, as late as 2012, was dedicated to documenting the exact emulator, plugin and settings combination necessary to get each and every game to at least a playable state, if at all possible. This necessitated having all of these emulators and sometimes even older or modified versions of them, along with a great many plugins, to be able to play most of the N64 library with the least amount of issues possible - though admittedly a good amount of games (particularly the most popular ones) were playable with just the best few of them. Each had advantages and disadvantages, and some games worked well in one only to not work in another, even when using the same plugin configuration. Of these, the big three emulators were Project64, 1964 and Mupen64.

Historically, the majority of N64 emulators all shared the same plugin spec (known as the zilmar spec, after the creator of Project64, the first emulator to use it), and could therefore all use the same plugins, meaning you could take a plugin DLL file, use it on one emulator, then take that DLL and use it on another, and it would also work there.

As for the terms HLE and LLE, which will occur with frequency throughout this page, and the difference between them, it is recommended to read this page on High/Low level emulation beforehand. To understand the current plugin situation, and why there are several competing emulators that all appear to use the same plugins but said plugins are not compatible across emulators, a bit of history is in order.

Retroarch best n64 emulator