Stockfish 19 Now Powers Game Analysis on ChessDada
By the ChessDada Team · Updated 6 November 2026 · 9 min read
The short answer
Every analysis tool on ChessDada now runs Stockfish 19, the newest version of the world's strongest open-source chess engine. That covers the free Chess Analysis Board and the Game Review that opens after every game you play here. The engine runs inside your own browser, the first download is about 2 MB instead of the old 7 MB, and in our own tests it found the best move more often and made fewer large errors than the Stockfish 18 build it replaces.
Stockfish is a free, open-source chess engine — a program that looks at a chess position, searches millions of possible continuations and tells you which move it thinks is best and by how much one side is ahead. It has been the strongest engine in the world for most of the last decade, it wins the major computer chess championships, and it is the engine behind the analysis features on most chess websites.
Stockfish 19 was released by the Stockfish team on 5 September 2026. It is the successor to Stockfish 18, which came out at the end of January 2026. Like every Stockfish release it is free for anyone to use, and the source code is published under the GNU General Public License.
For a player, the version number matters for one practical reason: a stronger engine gives you a more reliable verdict on your own games. When the engine tells you that move 23 was the mistake that lost the game, you want that verdict to be right.
What Is New in Stockfish 19
According to the official release notes from the Stockfish team, the main changes are:
More playing strength. The Stockfish team's testing shows Stockfish 19 gaining up to 44 Elo over Stockfish 18, and winning more than three times as many game pairs as it loses against it.
A new neural network design, SFNNv16. Stockfish evaluates positions with a neural network (known as NNUE). The new design removes redundant "threat" features, which makes the program smaller, and adds new pawn-pair features, which makes it stronger.
The secondary "small" network is gone. Since Stockfish 16.1 the engine had used a second, smaller network in some positions. Stockfish 19 drops it, which the team says helps exactly in the positions where the small net used to be weaker.
Better training. The network was trained with quantization-aware training on hundreds of billions of positions, rescored with a strong Leela Chess Zero network.
Universal binaries. On desktop computers you no longer have to pick between builds such as AVX2 or AVX-512: one download detects your processor and uses the fastest code path automatically.
More platforms, including WebAssembly. Official support was added for RISC-V and LoongArch processors and for WebAssembly targets — the technology that lets a chess engine run inside a web browser, which is how ChessDada uses it.
Stricter input checks. Positions, FEN strings and commands are validated more carefully, so a malformed position is rejected instead of being analysed silently.
Note on the "44 Elo" figure: that number is the Stockfish team's result for the full engine in their own test conditions. It describes how much stronger the new version is than the old one, not how strong the engine is against people — every recent Stockfish is far above any human player.
Where ChessDada Uses Stockfish 19
Since 5 November 2026, Stockfish 19 is the default engine in two places on ChessDada:
Analyse any position or complete game: paste a FEN or PGN, set up a position by hand, or load one from a picture of a board. Shows the best move, the evaluation and up to five candidate lines.
Goes through a game you played on ChessDada move by move, marks inaccuracies, mistakes and blunders, shows the best line you missed, and gives both players an accuracy score.
From the game-over card after a game, or from the games list on your player profile.
Both tools keep Stockfish 10 as a backup. If your browser cannot run the newer engine — for example on an old phone, or in Game Review when data-saver mode or a very slow connection is detected — the page switches to Stockfish 10 automatically, so the analysis still works. On the Analysis Board you can also choose the engine yourself in Settings.
The Play vs Computer mode is separate: there the engine is your opponent and its strength is turned down on purpose for each level, so it does not need the newest version.
The Browser Version: Why "Lite"?
The full Stockfish 19 is a desktop program with a large neural network file. To run in a web browser on a phone, ChessDada uses the Stockfish 19 lite build from the open-source stockfish.js project, which compiles Stockfish to WebAssembly. "Lite" means it carries a smaller neural network, so it downloads quickly and runs comfortably on a phone. It is not as strong as the full desktop engine with its big network, but it is still far stronger than any human player.
What this means for you:
Smaller download. The engine file is about 1.8 MB (about 1.2 MB compressed), compared with about 7.3 MB for the Stockfish 18 lite build we used before. On a mobile connection the first analysis starts noticeably sooner.
Downloaded once. After the first visit your browser keeps the engine, so the next analysis starts without downloading it again.
Private. The engine runs on your own device. The positions and games you analyse are not sent to a server to be evaluated, and the Analysis Board keeps working even if your connection drops after the page has loaded.
Battery. Because your own phone does the thinking, very long analysis uses more battery. A normal game review is over in a minute or two.
Our Own Test: Stockfish 19 vs Stockfish 18
We did not switch engines just because the number went up. Before changing anything, we compared the two browser builds on real positions from games played on ChessDada.
Test 1: 40 positions from real ChessDada games
We took 40 positions from the middle of real games (between move 8 and move 30). Each browser engine was given 1 second per position — roughly what it gets in Game Review. The answer was compared with a stronger reference: the full desktop Stockfish engine (version 16, with its large network) thinking for 3 seconds.
Measure (40 positions)
Stockfish 18 lite
Stockfish 19 lite
Found the reference best move
31 of 40
33 of 40
Average loss vs the best move
7.5 centipawns
4.2 centipawns
Big errors (1 pawn or more)
1
0
Engine download
about 7.3 MB
about 1.8 MB
A centipawn is one hundredth of a pawn. An average loss of 4.2 centipawns means that when Stockfish 19 lite did not pick the very best move, the move it picked was almost as good.
Test 2: a 20-game match
We then let the two browser engines play each other: 10 different openings, each played twice with colours reversed, at a fast 0.2 seconds per move. Stockfish 19 lite won 11.5 to 8.5 (4 wins, 1 loss, 15 draws).
Being honest about the numbers: 40 positions and 20 games is a small test, and a few results either way would change the figures. What it shows is that the new build is at least as good as the old one on the kind of positions ChessDada players actually reach — while being a quarter of the size. For the large-scale strength numbers, see the Stockfish team's own testing.
How to Review Your Game, Step by Step
Finish a game in the ChessDada lobby. When the game-over card appears, open the replay of the game. You can also open any past game from the games list on your player profile.
Press Analyze with Chess Engine. Stockfish 19 goes through the game move by move. You see the progress while it works, and a full game is usually done in a minute or two.
Look at the evaluation bar next to the board. It shows who is better after every move, from White's point of view.
Check the marked moves: inaccuracies, mistakes and blunders. For each one the review shows an arrow with the move the engine preferred and the best line that follows.
Read the game report: an accuracy score for both players, counts of each kind of error, and separate accuracy for the opening, middlegame and endgame. Book moves from known openings are not counted in the overall accuracy, so a memorised opening does not inflate the score.
Use Play vs computer from here on a position where you went wrong, and try to find the better plan against the engine.
Press Self analysis to try your own ideas: move the pieces freely, build variations, and watch Stockfish 19's top three lines and arrows update live.
Use Share & export to copy a link to the game (or to one exact move), the FEN or the PGN, or save the position as a picture or the whole game as an animated GIF.
♔ Analyse a position with Stockfish 19 now
Free, in your browser, no sign-up. Paste a FEN or PGN, set up a position by hand, or load one from a picture of a board.
The Chess Analysis Board works for any game, not only games played on ChessDada — a game from a tournament, a position from a book, or a puzzle you are stuck on.
Paste a FEN in the Position tab and press Load to analyse one position.
Paste a PGN to load a whole game, then step through it with the arrow buttons or the arrow keys while the engine evaluates each position.
Edit board lets you place pieces by hand, choose whose move it is and set castling rights. The board checks that the position is legal before the engine looks at it.
From image reads a screenshot of a chess board (upload it, or paste it with Ctrl+V) and turns it into a position for you to check and confirm. The picture is recognised inside your browser and is not uploaded.
In Settings choose how many candidate lines to show (1, 2, 3 or 5) and which engine to use.
For a composed puzzle, the engine reports a forced mate as a mate score, for example "Mate in 2", together with the moves — a quick way to check your answer to the daily puzzle.
How to Read the Engine's Numbers
What you see
What it means
+1.0
White is about one pawn better.
-2.5
Black is about two and a half pawns better.
between -0.5 and +0.5
Roughly equal.
above +2.0 or below -2.0
Usually winning for that side with accurate play.
M3 / Mate in 3
A forced checkmate in three moves.
Depth
How far ahead the engine has searched. Early numbers at low depth are rough; the evaluation settles as the depth climbs.
Several lines
If the first line is much better than the second, there was only one good move. If they are close, several moves were fine.
What an Engine Cannot Tell You
Stockfish 19 is a superb judge of a position, but it is not a coach. Keep three things in mind when you review your games:
It does not know why you played a move. A move marked as a mistake may have come from a missed tactic, a wrong plan or simply time trouble. Working out which one it was is the part that makes you stronger.
Engine moves are not always human moves. Sometimes the best move is a line no person would find over the board. If the engine's suggestion makes no sense to you, look for the second or third line, or try the position with Play vs computer from here.
Accuracy is not rating. A high accuracy score in a short, one-sided game is easy; a lower score in a long, complicated game can still be a very good performance.
The best habit is simple: before you open the engine, spend two minutes deciding where you think the game turned. Then let Stockfish tell you if you were right.
Stockfish 19 is the newest version of Stockfish, the free and open-source chess engine that has been the strongest in the world for most of the last decade. It was released by the Stockfish team on 5 September 2026. According to the team's testing it gains up to 44 Elo over Stockfish 18, thanks mainly to a new neural network design called SFNNv16.
Does ChessDada use Stockfish 19?
Yes. Since 5 November 2026 the Chess Analysis Board and the Game Review on ChessDada both use Stockfish 19 by default. It runs inside your browser as a WebAssembly build. Stockfish 10 stays available as an automatic backup for devices that cannot run the newer engine.
Is Stockfish 19 analysis free on ChessDada?
Yes. Both the Chess Analysis Board and Game Review are completely free. The Analysis Board does not need an account at all; Game Review is available for every game played on ChessDada.
What is the difference between Stockfish 19 and Stockfish 19 lite?
Stockfish 19 lite is the same engine with a smaller neural network, built so it can download quickly and run inside a web browser on a phone. It is not as strong as the full desktop program, but it is still far stronger than any human player. ChessDada uses the lite build because the engine runs on your own device.
Is Stockfish 19 better than Stockfish 18 for analysis?
In the Stockfish team's testing the full Stockfish 19 is up to 44 Elo stronger than Stockfish 18. In our own smaller test of the two browser builds on 40 positions from real ChessDada games, Stockfish 19 lite found the best move 33 times against 31, had a lower average error (4.2 against 7.5 centipawns), and made no big errors against one - while being about a quarter of the download size.
Are my games uploaded when I analyse them?
No. The engine runs inside your own browser, so the positions you analyse are evaluated on your device and are not sent to a server for analysis. Even the From image feature on the Analysis Board reads the picture inside your browser.
How do I review my game with Stockfish 19?
Finish a game on ChessDada, open the replay from the game-over card or from your profile's game list, and press Analyze with Chess Engine. Stockfish 19 marks inaccuracies, mistakes and blunders, shows the best line for each, and gives both players an accuracy score with separate figures for the opening, middlegame and endgame.
The browser build is Stockfish 19 lite from the stockfish.js project (version 19.0.1). Stockfish is free software under the GNU GPL version 3.
The Stockfish logo in the share image is by Klein Maetschke, from Wikimedia Commons, licensed under the GNU GPL version 3 or later / CC BY-SA 4.0. ChessDada is not affiliated with the Stockfish project.
Our comparison used 40 middlegame positions from real ChessDada games, 1 second per position for each browser engine, with desktop Stockfish 16 at 3 seconds per position as the reference; and a 20-game match (10 openings, colours reversed) at 0.2 seconds per move. Tests were run on our own server on 5 November 2026.
Final Thoughts
An engine upgrade is invisible until you need it — the moment you open a lost game and want to know exactly where it slipped away. With Stockfish 19 doing the checking, that answer is now faster to load and more reliable than before, and it still costs nothing and never leaves your device.
Play a game in the ChessDada lobby, then open the review and see what Stockfish 19 thinks. Or paste any position into the Chess Analysis Board right now.