AutoRegLib Mod for Minecraft 1.19.3, 1.19.2, 1.19.1 and 1.19, is what is known as an “add-on mod”, as its sole function is to allow other mods to run. Basically, the creator has taken it upon himself to modify a part of Minecraft’s code, making it easier for mod makers to use.
In other words, AutoRegLib facilitates the creation and further development of mods, making both the first version and subsequent updates more affordable. However, it obviously makes no sense to install it on its own.
And little more to say, its function is quite simple and obvious, to allow mod developers to avoid having to spend so many hours on each update. The creator has taken care to create and enhance a level of abstraction, to more easily record new content.
All of this allows for the creation of new features, exclusively related to mod and add-on developers, so again it is important to stress that it does not add new content. That is, it will always require at least one other mod to be minimally functional.
This add-on has been installed by more than a hundred million people and is one of the most downloaded and used mods with every version of the game. It is also perfectly compatible with the vast majority of mods, so installation on servers is usually no problem.