Free to play
Reactor Zero is free. The beta has no payments and no ads, and you unlock every hero by playing.
BROWSER CO-OP GAME · UP TO 3 PLAYERS
Free co-op game in your browser
Reactor Zero is a free online co-op game: gather up to three friends, pick your heroes and defend the core together against waves of enemies, all the way to the boss fight. It runs in the browser on computer and phone. No download and no installation.
No install • No ads during the beta • PL / EN / UA
WHY REACTOR ZERO
A co-op game you can join in a minute
No install
Open the page and play. It is a browser game for computer, tablet and phone with touch controls.
Up to 3 players online
Invite friends with a room code or join an open game. Co-op means combining roles: tank, sniper, medic.
Quick rounds
A round lasts a few minutes and ends with a boss fight. Perfect for a break or an evening together.
Try without an account
The quick test starts a solo game with bots right away, with no sign-up. You need an account for multiplayer and for saving progress.
No chat in the game
There is no open chat with strangers. Younger players are matched in public rooms only with peers (an account under 16 needs a parent's consent).
HOW IT WORKS
Defending the core together
Gather your team
Choose "Quick game" or create a room and send your friends the code. The game starts when the team is ready.
Pick your heroes
Five characters with different roles. The medic revives fallen allies, the sniper keeps distance, the guard takes the hits.
Defend the core
Waves of enemies come from every side. Every half a minute you pick upgrades, and after about two minutes the boss appears.
Claim the rewards
After a win you get chests (five rarity tiers), coins and account progress. You unlock more heroes and cosmetics.
HEROES
Five roles in one team
Meet all the heroes »
Zero
Viper
Bastion
Pulse
DashWHO IT IS FOR
Play with friends, with family or for a quick session
Looking for a co-op game you can play together right away, with nothing to buy or install? Reactor Zero combines top-down action, shared decisions and short rounds. It works as a game for an evening with friends, a break from work or some fun with your siblings. It is still an open beta: the game grows week by week and many changes come from player feedback. See what is new on the page News.
Frequently asked questions
Is Reactor Zero really free?
Yes. The game is free, and the open beta has no payments and no ads.
Do I need to install anything?
No. It is a browser game: just open the page in a browser on a computer, tablet or phone.
How many players can play together?
A team has up to three players. Bots fill the empty slots, so you can also play solo.
Do I need an account?
Not for the solo quick test. An account is needed for online play with others and for saving progress. You create it without an e-mail address, with just a nickname and a password.
Can I play on a phone?
Yes. The game has touch controls: the left side of the screen is movement, the right side is shooting, and buttons trigger the special ability and the dodge.
What is the age rating?
Accounts are for people aged 16 and over. Younger players can play with the consent of a parent or legal guardian. Details are in the Terms and the Privacy Policy.
Which languages does the game have?
Polish, English and Ukrainian. The language is set automatically from your browser and can be changed in the game menu.
What is a co-op game?
A co-op (cooperative) game is one in which players work together against computer-controlled enemies instead of fighting each other. In Reactor Zero you defend the core together.
READY FOR A TEAM ROUND?
Invite your friends, pick your heroes and see how long you can defend the core.
PLAY FOR FREEMultiplayer needs a player account. The quick test works without one.