Useful Website
This include many linksGeneral
Chess.com
chess24
There is no need for words. Popular website.
Game Watch
FollowChess
Lite and quick, easy to use. There is app version for smartphone.
ChessBomb
This website has unique feature. Every move is colored by evaluation. Blue is good, gray is fine, red is bad. Is it usefulness or to spoil the view? It depends on you.
Chessgames
Great DB! We can check ancient game like Greco and modern game.
TCEC
Top Chess Engine Championship is held at this.
PGN website
PGN Mentor
PGN sorted by players, openings and events.
BILL WALL'S CHESS PAGE
It include book's PGN.
Study
Chessable
Relatively new website. Many famous SGM published opening course in this website. Nepo, Giri, So and so on.
simplifychess
Good and many article.
YouTube
Twitch
Many GMs streams or upload videos. Very instructive and sometimes funny. Check it out.
Statistics
2700chess
We can check increase and decrease of top players rating. Also FIDE players.
CHESSMETRICS
There are correct rating in historical mean. Actually rating is inflation little by little. So Fischer's 2785 is not same modern GM's 2785. If you are interested, please visit this website.
Variants
PyChess
There are many variants.
Chess Variants Training
We can study variants puzzle and endgame.
In the end my video (:
Thank you for reading.
https://www.youtube.com/watch?v=26-rZdzrY6c