Chess.com puzzles, Lichess Puzzle Rush, and OP.GG built online puzzle communities around Elo-rated tactical problems. Here is how the rating systems work and why chess went mainstream after 2020.
Chess.com had 50 million registered users in early 2020. By the end of 2023, it had over 150 million. Lichess, the free and open-source alternative, grew from roughly 1 million monthly active users to over 5 million in the same period. The catalyst was a combination of pandemic lockdowns, the Netflix series The Queen's Gambit, and a surge of streamers playing chess on Twitch.
The growth was not just in casual play. Puzzle solving, the practice of working through tactical positions with a single best move, became a daily habit for millions of players. Chess.com's puzzle system and Lichess's puzzle database both use Elo-style rating systems to match puzzles to player skill. The result is an endlessly self-adjusting difficulty curve that keeps players engaged.
OP.GG, a site built for League of Legends stat tracking, followed a different path to the same destination: a community organized around analyzing and solving problems. You can decode chess positions with the PGN/FEN Decoder and work through logic puzzles with the Sudoku Solver.
Both Chess.com and Lichess rate puzzles using a Glicko-2 rating system, a refinement of the Elo system designed by Mark Glickman. The puzzle has a rating. The player has a rating. When the player solves a puzzle, their rating goes up and the puzzle's rating goes down. When the player fails, the reverse happens. Over millions of attempts, each puzzle converges on a rating that reflects the difficulty players actually experience.
The rating is not assigned by a human. It emerges from the data. A puzzle that 80% of 1500-rated players solve but only 30% of 2000-rated players solve will settle around 1800. This is the same principle used for player ratings in competitive chess, adapted so that the puzzle is treated as an opponent.
Chess.com generates puzzles from real games. The system scans the Chess.com game database for positions where one side has a forcing sequence (a series of checks, captures, or threats that limit the opponent's responses) and extracts the position as a puzzle. The "best move" is determined by engine analysis. Lichess does the same thing using its own game database, which is publicly available. The Lichess puzzle database is open source and contains millions of rated puzzles.
The rating system creates a feedback loop. Players solve puzzles at their rating level, improve, get harder puzzles, and repeat. This is the same engagement structure that makes Wordle and Connections sticky, but applied to a skill that has a measurable progression curve.
The puzzles on Chess.com and Lichess are almost entirely tactical. A tactical puzzle presents a position where a forcing sequence leads to a concrete advantage: winning material, delivering checkmate, or achieving a promotion. The solution is verifiable. There is a single best move (or a single best sequence), and the engine confirms it.
Positional puzzles are different. A positional puzzle asks the player to choose a plan: where to place the knights, which side of the board to attack, whether to trade a bishop for a knight. These are harder to generate and harder to rate because there is rarely a single verifiable best answer. Chess.com has experimented with positional exercises, but they have not become popular because the feedback loop is weaker. A player who gets a tactical puzzle wrong knows immediately what they missed. A player who chooses the wrong plan in a positional exercise may not understand why for several moves.
This is why puzzle communities form around tactical puzzles. The binary feedback (solved or failed) creates a clear signal. The rating system converts that signal into a number. The number creates a leaderboard. The leaderboard creates competition. The Chess.com puzzles page and the Lichess puzzles page both display leaderboards sorted by puzzle rating.
Puzzle Rush, a Chess.com game mode where players solve puzzles against a clock with three lives, adds a time-pressure element. Puzzle Battle, a head-to-head version where two players race through the same puzzle set, adds direct competition. Both modes use the same underlying puzzle database but change the framing from "solve this" to "solve this faster than someone else."
Chess.com's growth from 50 million to 150 million users between 2020 and 2023 had three drivers.
The first was the pandemic. Lockdowns sent people indoors looking for online activities. Chess, being free to play and requiring no physical equipment, fit. Lichess saw similar growth. FIDE, the international chess federation, reported a spike in online tournament participation during 2020 and 2021.
The second was The Queen's Gambit, a Netflix miniseries released in October 2020 about a fictional chess prodigy. The show was watched by over 62 million households in its first 28 days, according to Netflix. Chess.com reported a spike in new signups immediately after the show's release. The show made chess culturally visible in a way it had not been since the Bobby Fischer era.
The third was streaming. Chess streamers on Twitch and YouTube, including Hikaru Nakamura (a grandmaster), Levy Rozman (GothamChess), and Eric Rosen, built audiences in the hundreds of thousands. Rozman's channel grew from roughly 100,000 subscribers in early 2020 to over 4 million by 2023. Streamers played puzzles live, explained their thought process, and turned puzzle solving into spectator content.
The Chess.com blog and the Lichess documentation both document the platform's growth and features. FIDE publishes rating data and tournament results at fide.com.
OP.GG is a different kind of puzzle community. The site, launched in 2012, provides match data, rankings, and analysis for League of Legends players. You enter your summoner name and see your match history, your win rate per champion, your rank progression, and your performance relative to other players at your skill level.
The connection to puzzles is indirect but real. League of Legends is a game of incomplete information: you cannot see the enemy team's positions unless they are near your units or in your vision range. Analyzing a match after the fact, working out what went wrong and what the optimal decision was at each point, is a puzzle-solving exercise. OP.GG provides the data that makes that analysis possible.
The site expanded beyond League of Legends into Valorant, Overwatch, and other competitive games. The pattern is the same: provide detailed post-match data, let players analyze it, and build a community around the analysis. The Kakuro Solver and the Mastermind Solver cover the same analytical territory in a different format: constrained problems where you work backward from partial information to find the solution.
OP.GG's user base is estimated at over 50 million monthly visitors. The site is free, with a premium tier that removes ads and adds advanced analytics. The community forms around the data: players share their OP.GG profiles in forums, ask for advice, and use the match data to improve. The puzzle is "what should I have done differently," and the data is the set of clues.
Chess.com, Lichess, and OP.GG all built communities that outlasted their initial growth spikes. The common element is a rating or ranking system that gives players a persistent identity. Your puzzle rating on Chess.com is a number that reflects your skill. Your rank on OP.GG is a tier that reflects your performance. These numbers give players a reason to come back: to maintain their rating, to climb a leaderboard, to compare themselves to friends.
A puzzle without a rating system is a one-time experience. A puzzle with a rating system is a long-term project. This is the structural difference between Wordle (which has no rating, just a daily result) and Chess.com puzzles (which have a persistent rating). Wordle's retention comes from the daily ritual and social sharing. Chess.com's retention comes from the rating progression. Both work, but they work for different reasons and different player types.
The implication for anyone building a puzzle platform is that you need at least one of these mechanisms. A daily ritual creates social engagement. A rating system creates personal progression. Without either, players solve a few puzzles and leave.
Chess.com rates puzzles using the Glicko-2 system, a refinement of Elo. The puzzle and the player both have ratings. Solving a puzzle raises the player's rating and lowers the puzzle's. Failing does the opposite. Over millions of attempts, each puzzle converges on a rating reflecting the difficulty players experience.
Lichess scans its game database for positions with forcing sequences (checks, captures, or threats that limit the opponent's responses) and extracts them as puzzles. The best move is determined by engine analysis. The puzzle database is open source and available on GitHub.
Three factors drove the chess boom: pandemic lockdowns sent people indoors looking for online activities, the Netflix series The Queen's Gambit made chess culturally visible, and chess streamers on Twitch and YouTube turned puzzle solving and gameplay into spectator content.
OP.GG is a website launched in 2012 that provides match data, rankings, and analysis for League of Legends and other competitive games. Players enter their summoner name to see match history, win rates, and rank progression. The site has an estimated 50 million monthly visitors.
Tactical puzzles present a position with a forcing sequence that leads to a concrete advantage, and the solution is verifiable by engine analysis. Positional puzzles ask the player to choose a plan (where to attack, what to trade), and there is rarely a single verifiable best answer, making them harder to generate and rate.
PGN / FEN Chess Notation Decoder
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