Comment by brynnbee

I made the old MMO EverQuest but in a browser, complete with a custom server built from the ground up. It's in a bit of a state of transition right now and sorta buggy, but:

https://www.idlequest.net/

It shares the neat feature of the HL2 project in that it doesn't need any installation, and it downloads zone files (which aren't huge) as needed. It can also run around and kill/loot things automatically for you!