https://lichess.org/ https://lichess.org/ It's the best online chess platform by far - super slick and fast UI, lots modes and tournaments, analysis tools, man

https://lichess.org/ https://lichess.org/ It's the best online chess platform by far - super slick and fast UI, lots modes and tournaments, analysis tools, many of the best players in the world play there frequently. It's open source and completely free, miles ahead of any paid competitor and the team behind it seem to have admirable integrity and insist on making a great product instead of selling out. (No idea how it ranks on the "known-unknown" scale, it's obviously a popular website but not the first thing that comes to mind when I think of FOSS.)