It's planned for Alpha 6, what you are currently playing is Alpha 3 and we're working on Alpha 4. So... Soon! https://developer.valvesoftware.com/wiki/Valve_Time
Chrome and Safari are the recommended browsers but the game works in Firefox and Opera as well. The game does not work in Internet Explorer because Internet Explorer does not support many of the modern standards that the other browsers do. So for that reason we made the decision to not allow playing the game in Internet Explorer because it would severely impact the way people perceive the game. - To make the game IE compatible we would have had to remove a lot of the cool aspects of the game and made it into something that would not have been very enjoyable for anyone. I used to be the biggest Internet Explorer fan-boy but over the years IE has fallen way behind the speed and features of the other browsers.
A game mode called 'quick deathmatch' is in the making. Here you can join a game that's already in progress. Also some feedback to how many people are online in which game modes and other tweaks are on the agenda. But first our programmers will have a christmas holiday. Then we'll get right back to it! :)
Ok...there is honestly still hardly anyone playing multiplayer from my point of view...dosen't mean there ain't anyone playin multiplayer, since I keep trying to get a match going, and nobody is joining in. One person joins in after awhile, then that person leaves after losing patience for the other people to show uo.
THe multiplayer would be more enjoyable if more people would play it...but the single player mode has no upgrade option for the tanks, since you get to choose tier 3 tanks...but you can't upgrade them. So if only more people would play on multiplayer mode, then this game would be more enjoyable.
 "SideQuest"){kind=icon}
 "Hero Manager"){kind=icon}
 "Dude Quest"){kind=icon}
 "Battle without End"){kind=icon}
 "Burrito Bison Revenge"){kind=icon}
 "Worlds Quest"){kind=icon}
 "Valthirian Arc 2"){kind=icon}
 "Company of Tanks Beta"){kind=icon}
 "Super Duck Punch!"){kind=icon}
 "Arkandian Revenant"){kind=icon}
Some people have trouble installing unity on certain browsers. If you switch to another browser you may have better luck!