I have to be the responsible demon hunter here. Private servers come with baggage:
Unlike games with leaked server files, Diablo 3 was built from the ground up to keep almost all data (monster AI, loot drops, and environmental triggers) on Blizzard's servers. diablo 3 private server
In the modding community, the most popular way to play isn't connecting to a third-party server, but running a local patch that bypasses the login screen. This allows players to access a "local server" on their own machine. This is often the preferred method for those who want to use popular mods like: I have to be the responsible demon hunter here
Despite Diablo III having a "massive player base" that still reaches millions according to Blizzard, private servers offer unique benefits: This allows players to access a "local server"
: Emulators completely bypass the controversial, discontinued marketplace. Notable Projects and Emulation Software
Here is everything you need to know about the history, current status, and technical reality of Diablo 3 private servers. The History of Diablo 3 Private Servers