Illegal castling

In this bullet game, I think I was able to castle when it was illegal. Is this right?

no it was legal. the king cannot pass through check but the castle can

Interesting, I'd never seen this. Thanks!

That is a legal castle.

When is a castle illegal?
* If the rook you want to castle has been moved
* If your king has been moved
* If you are in check
* If the squares which your king uses to castle are under attack

In your game the c8 and d8 squares were not under attack, allowing you to castle.

so what about this? (last move)

The rule is taught wrongly so often that it's made its way to the contact page under "bug":
lichess.org/contact#help-castling

Edit: just noticed the hyperlink "this interactive game" links to the en passant tutorial. Should link to lichess.org/learn#/14 instead.

@mohamadreza1386 That's a "from position" game with long castling allowed for black. It's basically 960 castling in that game:
en.wikipedia.org/wiki/Chess960#Castling_rules

I can see that you've created that game. The black king is already castled, so if you want to continue a normal game, uncheck Black O-O and Black O-O-O on the board editor before continuing the game from the position.

@DoTheMath Yes, I was so sure that I knew the correct rule as "no square involved in castling, from king to rook included, should be under attack" (it's been about 30 years and I never encountered that rare situation where the difference matters), I didn't even read that castling article until the end... Thanks!

@vieille can white castle here?

@Nordlandia Guess so. *Should* white castle is another issue.