Are there some free chess game databases where it is possible and allowed to download games? Is it possible to use this information for my own purposes? For example, would be allowed to make a machine learning app that learned from the downloaded games?
Caïssabase is one of the biggest and best.
From the website:
What is Caïssabase?
When I got back into Chess a year or two back I couldn't find a decent free regularly updated database of Chess games.
There are some good ones out there like Kingbase and Millionbase (not updated anymore).
What is in Caïssabase?
CURRENTLY 4.02 MILLION GAMES
I started from the following databases/sources.
I then merged in all of the TWIC back issues up to the date on the archive as well as all the master games from pgnmentor.
What about curation? Glad you asked. Roughly I followed these rules.
- Removed all duplicates
- Removed all games with less than 5 moves
- Aimed for all games to have one (or both) players at least master strength
- Fixed names and event spellings where possible
- Inserted ELO's where known
Inserted extended ECO opening codes
Where I live facts are not copyrightable, Chess moves played in a game are facts.
You'll notice there are no comments on any of the games as comments are copyrightable.
The latest download is from September 2019, so perhaps the intention of a monthly download is proving a bit too much. Meanwhile I've downloaded it for use with Scid vs PC and will be a grateful user.
I would add the Lichess Elite Database to the list :-) It is the best of lichess games: only higher-rated players in "decent" time controls (aka no bullet).