Caissa is an online chess platform with a strong correspondence chess component alongside classical online play, puzzles, and a set of auxiliary tools. For correspondence chess specifically, Caissa hosts rated games and tournaments where players can take hours or days per move, with support for engine-assisted analysis in keeping with the correspondence tradition.

The platform also provides a collection of utility tools including a game analysis board, position editor, FEN/PGN utilities, and opening resources. The interface is clean and modern compared to older correspondence servers, and the platform has been actively developed with new features added regularly.

Caissa offers a free tier and premium membership options. It is a good choice for players who want a modern correspondence chess experience or who want a single platform that combines correspondence play with useful analysis tools.