OGS uses glicko2 as rating system. https://en.m.wikipedia.org/wiki/Glicko_rating_system#Determination
Here an approximation of how the rating system works:
- Each player has a rating (500-3500) and a deviation (indicated by ±)
- After one of your games ends, we take the last 15 games to calculate, how your rating has to change to better predict the outcome of those games.
- The difference of you rating and your opponents rating gives an estimation for how probable it is for each player to win the game.
- For each game the win probability, the outcome (win/lose/draw) and your deviation determine how your rating changes.
Here the ranks of the OGS player base (copied from @S_Alexander’s thread)
