This page documents known Bugs that have been found in the game.
If you look at the server list, occasionally, 1 server may say it has null/undefined players instead of the usual x/40 or x/80 players. Happened to multiple people, including ThePokegeek5000 on server 22.214.171.124
No Age 9 ItemsIf a Player selects the Polearm, he will never be offered any upgrades at Age 9. This is a bug carried over from the Musket that was never fixed, as the Musket was moved up in Age instead. Occurs on all servers.
No Age 7 Item Usage
There is a glitch, that if you get Mine at Age 5, and something that is not Castle Wall at Age 7, you won't be able to use your Age 7 item, due to you having more that 9 items on your hotbar. Number Keys and the Clicking don't work.
Experimental servers not working
As of version 0.897, when you tried to connect to experimental servers, a message pops up saying bundle not found could be an issue with the party key. This error occured on all browsers, even if extensions/add-ons were disabled. The experimental servers also appeared to be almost empty with only 4 people in all the 15 servers. This glitch was patched a day later.
Bull Helmet HP Drain
There is a glitch that happened in the 0.88 Update, in which the Bull Helmet drains no HP. It happens on Many (Maybe All) Servers.
There was a glitch in Moomoo.io as of 0.87 that the player may not be able to see any player, what they are holding, including themselves. They can still see names and HP bars, and animals. The game may also freeze for a minute. While active, you can not buy any hats or accessories. It will toggle on and off.