Stockfish 19: what's new and where to use it

Stockfish is a chess engine: a program that calculates chess positions and returns an evaluation and a best move. It has no board and no buttons of its own. It is a command-line program that talks to other software through UCI (Universal Chess Interface), a standard text protocol. Chess programs, websites and apps put a board on top of it and show its results.

Stockfish is developed by volunteers as an open-source project under the GPLv3 licence. Anyone can read the code. New ideas are tested on Fishtest, a testing framework to which volunteers donate computer time, in many thousands of engine games before they are accepted. Since Stockfish 12 in 2020, the engine evaluates positions with a neural network called NNUE. It runs efficiently on an ordinary processor, so no graphics card is needed.

The Stockfish team lists these changes in the Stockfish 19 release announcement:

• Playing strength. Up to 44 Elo stronger than Stockfish 18 in the team's tests. Stockfish 19 wins more than three times as many game pairs as it loses against Stockfish 18. A game pair means the same opening is played twice, once with each colour.
• New network architecture, SFNNv16. Redundant threat features were removed, which makes the program smaller. New features describe pairs of pawns.
• One network instead of two. The second, smaller network that Stockfish 16.1 introduced has been retired.
• Better training. The network was trained with quantization-aware training (QAT). Hundreds of billions of training positions were rescored with a strong network from Leela Chess Zero (Lc0).
• Universal binaries. The download detects the features of your processor when it starts and runs the best code for it. You no longer have to choose between builds such as AVX2 or AVX-512.
• More platforms. Native support for RISC-V (RVV) and LoongArch processors, 1 GB huge pages on Linux, and new WebAssembly targets. WebAssembly is the format that lets an engine run inside a web browser.
• Stricter input checks. Positions, FEN strings and UCI commands are validated more strictly. On invalid input, Stockfish prints info string CRITICAL ERROR with the command and the reason, and then quits. A good chess program prevents such input in the first place.

If you use Stockfish through an app or a website, most of this is invisible. What you notice is a stronger engine. The network format and the binaries matter mainly to developers and to people who run the engine on their own computer.

Sources: the release announcements for Stockfish 18 and Stockfish 19. The Elo gains come from the team's own tests of one Stockfish version against another. They do not describe games against people.

Much stronger than any human player. Already with Stockfish 18, the team wrote that the engine is stronger than any human, even on older or low-end hardware. For a number, independent rating lists for engines are the best reference. On the CCRL 40/15 rating list of 16 October 2026, Stockfish 19 (64-bit, 4 CPU cores) is in first place with 3650 Elo, plus or minus 17. Several other engines are within a few points, so the order at the top can change from one update to the next.

Read that number with care. CCRL ratings come from games between engines under fixed conditions: time control, hardware and opening book. They form a scale of their own and cannot be compared with a FIDE rating or with your rating on Lichess or Chess.com. How Stockfish's strength can be limited, and what its Elo settings mean, is explained in Stockfish Elo and levels.

In practice, strength also depends on your device and the time per move. A fast computer searches deeper in one second than an older phone. For checking your own games, this difference is usually small: the mistakes that decide games between people show up quickly on any current device.

You can use Stockfish 19 without installing anything. On our page play against Stockfish, the board at the top runs Stockfish 19 directly in your browser, at the same five levels as the app. To keep the download small, it is a smaller WebAssembly build with a smaller network than the full engine, and its speed depends on your browser and device. That is enough for a game at the five levels, but it is not the full strength of Stockfish 19.

Lichess also offers an analysis board with Stockfish 19 in the browser, according to its features page. For deep analysis on a phone or tablet, or without a connection, an app that runs the full engine on the device is the better choice.

ChessWOW includes Stockfish 19 with its full network and runs it on your device, offline. You do not need to install an engine or a separate chess program: board, engine and analysis come together in one app. Positions come from a photo, a screenshot, a book diagram, the board editor or a game imported from Chess.com or Lichess. How to read the evaluation and the lines is explained in Stockfish app offline.