Today we're officially introducing a special type of user account: Bots.

Lichess Bots are for:

Connected physical boards (EDIT: we have a newer, better API for that now!)

Vote chess programs (letting spectators vote for the next move to play)

Custom chess clients (EDIT: use the new Board API instead)

Chess engines

Cyborg/Centaur chess (man and machine teaming up)

Anything you can think of that can play chess

Lichess Bots can:

Play casual and rated games with other players

Send and accept challenges

Follow and be followed by other players

Lichess Bots cannot:

Participate in tournament or simuls

Use lobby seeks or pools

Appear in leaderboards

Credit: Matīss Apinis

Who are these bots for?

Engine developers

You can use a lichess bot to try out your engine against actual players, and other engines. If your engine supports the UCI or XBoard protocol, you're in luck! Download the official lichess-bot client and you will be all set in no time.

UI developers

To interface your chess client or physical board with lichess, use the lichess bot HTTP API. Here's a JavaScript reference implementation and the OAuth Personal Token creation page.

EDIT: We have released a new Board API for interfacing with human-operated clients.

Chess players

No need to be a coder to enjoy playing chess with bots! Here's a list of famous bots you can challenge for great chess fun:

More links

Bots Team to meet other bot owners.

Discord channel to get help with the API or the existing clients.

Bots TV to watch the current strongest bot game.

Bot HTTP API to build your own bot.

Board API to play on Lichess with an e-board or a third-party client.

Frequently asked questions

Can bots play rated games?

Yes. However players only win or lose half rating points during rated games with bots.

Why do player ratings even change? Shouldn't the bot rating only be affected?

We don't play casual games the same way we play rated games. In order for the bots to get reliable ratings, we need their opponents to play their best, and that means putting their own rating on the table.

A couple years ago, we tried to give the "Play with the machine" levels actual ratings. It didn't work, because we don't play them seriously, because we don't lose rating to them.

Is it ok to cheat in a game with a bot?

No, it is a bannable offense. Just like cheating in a game with any normal user. If you want to use computer assistance or play Centaur chess, create a Bot account.

Similarly to games with normal users, an exception can be made in casual games, after obtaining the explicit consent of the opponent.

Many bots will be strong engines. Won't they disrupt the rating system?

Creating a bot requires technical knowledge and we expect that they will remain a minority. As long as less than 0.1% of new accounts are bots, there won't be any visible change to the rating distribution. We'll keep an eye on it.

What about rating manipulation? One could create a bot to farm rating points out of it?

That is called sandbagging or boosting. You can do the same thing with a normal account. Lichess detects it and bans the offenders.

Will there be bot contests or tournaments?

Bot play cannot be competitive. No tournaments, no leaderboards, no trophies. Because it all boils down to who's got the biggest CPU to run Stockfish on. Only way we can have competitive engine play is by having lichess host the engines, in TCEC fashion, and we're not going to do that for a long time.

Why can't we use the API with our normal user accounts?

EDIT: With our new Board API, it's possible to use our normal accounts!

It would be awesome to open the play API for all, and have people create their own clients. In a perfect world, we would totally do it.

But in our world, we have to deal with cheating. It's a real problem, and we take it very seriously.

In our fight against cheat, we have two weapons. The first one is our server, where we evaluate the moves' quality, frequency, and other metrics. The second one is our client, where we gather more valuable metrics to identify cheaters.

If we open an API to directly access our server, then we're losing half of our defenses (which are located in our client).

That's the reason why only BOT accounts can use an API for playing on lichess. It's unfortunate, but defending fair play is our top priority.