Chess engine profile · Updated October 2026
Stockfish 19 The strongest chess engine in the world
Stockfish is a free, open-source chess engine that has dominated computer chess for over a decade. Version 19, released September 5, 2026, is up to 44 Elo stronger than Stockfish 18 in the developers’ tests and is number 1 on every major rating list, with 3650 on CCRL 40/15 — far above any human grandmaster. It uses the SFNNv16 neural network for evaluation. Play it here in your browser, take it with you in the Rama Chess app, or let it check your own games.
Stockfish quick facts (October 2026)
- Latest version
- Stockfish 19, released September 5, 2026. The version before, Stockfish 18, came out on January 31, 2026. There is no Stockfish 18.1.
- Stockfish 19 Elo
- 3650 CCRL 40/15 (4 CPU) · 3804 CCRL Blitz (8 CPU) · 3649 CEGT 40/20 (1 CPU) · 4116 CCRL Fischer Random. No. 1 on all of them. Every version’s Elo
- Stockfish 18 Elo
- 3649 CCRL 40/15 (4 CPU) · 3772 CCRL Blitz (1 CPU) · 3621 CEGT 40/20 (1 CPU)
- Stockfish 19 vs 18
- Up to +44 Elo and more than three times as many game pairs won as lost (Stockfish team tests). New SFNNv16 network, one network instead of two, universal downloads. Full comparison
- Download
- Free (GPLv3), only from stockfishchess.org/download or the Source code. Which file to pick
- Android / APK
- No official APK. The official Android files are engines for chess apps. Use an app with Stockfish inside (like Rama Chess) or play online.
Sources, checked October 15, 2026: CCRL 40/15 (computed Oct 9, 2026), CCRL Blitz (Oct 10), CCRL 40/2 FRC (Oct 4), CEGT 40/20 (updated Oct 11), Source code.
Play against Stockfish 19 online
Free, in your browser, nothing to install. The board loads only when you press play.
- Press playThe Stockfish 19 board opens on this page.
- Set up your gameChoose your side and your settings, then make your first move.
- Check the game afterwardsOpen the analyser to see where the engine got ahead.
Other top engines you can play here: Obsidian, Stormphrax, Reckless, PlentyChess, Viridithas, Berserk, Caissa, Koivisto, Ethereal. Licences and source code: chess engine licenses.
Download Stockfish 19 (official) and on your phone
Stockfish 19 is free. Get the engine only from the official site or source — or use it inside an app.
| You have | What to download |
|---|---|
| Windows, Mac or Linux | The “universal” file for your system from stockfishchess.org/download, then add it to a chess program (GUI). Step by step |
| Android phone | There is no official Stockfish APK. The official Android files (ARM64, ARMv7) are engines that a chess app loads. Easiest: an app with Stockfish built in, like Rama Chess below. |
| iPhone / iPad | No engine file. The official site recommends the SmallFish app. |
| Want Stockfish 18? | Still on the official Source code (January 31, 2026). Stockfish 19 is stronger. |
| No download at all | Play Stockfish 19 online or use the analyser in your browser. |
Rama Chess — play and analyse with Stockfish
Free Android app on Google Play
- Play Stockfish at full strength, or choose from 130+ chess bots at every level.
- Analyse your games with the engine and see the best move in every position.
- Train with puzzles, openings and the games of the best players.
Want the engine file itself for a desktop chess program? The official builds for Windows, macOS and Linux are at stockfishchess.org/download. “Stockfish APK” files on other sites were not made by the Stockfish team. All official download links.
Stockfish 19 Elo rating
Real numbers from the main engine rating lists, checked October 15, 2026
Stockfish Elo by version (CCRL 40/15)
How strong is Stockfish 19 really?
Why different numbers? Each rating list tests engines on its own hardware and time control and fixes its own scale, so 3650 on CCRL 40/15 and 3804 on CCRL Blitz are both correct. Compare engines inside one list only. More CPU cores also add strength: on CCRL 40/15 Stockfish 19 is 3650 with 4 cores and 3629 with 1 core.
Why is 19 only one point above 18 on CCRL? Top engines draw most games from normal openings (Stockfish 19 drew 92.6% of its 698 CCRL 40/15 games), which squeezes the top of the list, and the error margin is ±17. The Stockfish team tests with unbalanced openings, where Stockfish 19 gained up to 44 Elo over Stockfish 18.
Stockfish 4000 Elo? Only the Fischer Random list (4116) is above 4000. On the normal-chess lists Stockfish 19 is between 3649 and 3804. Sites that say “4000+” or “4050” for normal chess do not name a rating list.
And against humans? Magnus Carlsen’s peak of 2882 (FIDE, May 2014) is the human record. Engine lists and FIDE are separate pools, so the exact gap cannot be measured — but no top player has seriously challenged a top engine in an even match since Deep Fritz beat world champion Vladimir Kramnik 4–2 in 2006. Stockfish vs Magnus Carlsen · Stockfish Elo by version
Stockfish 19 vs Stockfish 18
The two latest major releases, side by side, from the official release notes. More detail: Stockfish 19 vs Stockfish 18 · Stockfish 18 vs 17
| Stockfish 19 | Stockfish 18 | |
|---|---|---|
| Released | September 5, 2026 | January 31, 2026 |
| Elo gain (Stockfish team tests) | Up to +44 over Stockfish 18 | Up to +46 over Stockfish 17 |
| Game pairs | More than 3 times as many won as lost vs Stockfish 18 | 4 times as many won as lost vs Stockfish 17 |
| CCRL 40/15 (4 CPU) | 3650 (No. 1) | 3649 |
| CEGT 40/20 (1 CPU) | 3649 (No. 1) | 3621 |
| Neural network | SFNNv16: redundant threat features removed, new pawn-pair features; the second, small network (added in 16.1) retired | SFNNv10 with the new ‘Threat Inputs’ features |
| Training | Quantization-Aware Training; hundreds of billions of positions rescored with a strong Leela net | Automated training recipes; over 100 billion positions of Lc0 data |
| Search and speed | Shared memory reworked for Linux, macOS and BSD; 1 GB Linux huge pages | ‘Correction History’ search; ‘Shared Memory’ for network weights; better at stalemates and fortresses |
| Download | One “universal” file per system that picks the best code for your processor | Separate builds per processor type (avx2, bmi2, avx512 …) |
| New platforms | RISC-V, LoongArch, WebAssembly | — |
| Licence | Free, open source (GPLv3) | Free, open source (GPLv3) |
Stockfish 18: Elo, release date and strength
Released January 31, 2026, and replaced by Stockfish 19 seven months later
Stockfish 18 came out on January 31, 2026. It brought the SFNNv10 network with its new ‘Threat Inputs’ features, a search refined with ‘Correction History’, and ‘Shared Memory’ for cloud analysis. Against Stockfish 17 it gained up to 46 Elo and won four times as many game pairs as it lost.
Stockfish 18 Elo: 3649 on CCRL 40/15 with 4 CPU cores and 3628 with 1 core, 3772 on CCRL Blitz (1 CPU) and 3621 on CEGT 40/20 (1 CPU) — lists checked October 15, 2026. On every list it is just below Stockfish 19. There is no Stockfish 18.1: after 18 the next official release was 19.
Stockfish 19 is up to 44 Elo stronger, so it is the version to play and analyse with today. On Rama Chess the play page and the analyser use Stockfish 19. Stockfish 18 can still be downloaded from the official Source code.
How Stockfish works
Two parts do the work: a very fast search and a small neural network
Alpha-beta search
Stockfish looks many moves ahead and cuts away the lines that cannot be best, so it spends its time only on the moves that matter. It checks millions of positions every second.
NNUE evaluation
A neural network that runs on an ordinary processor gives each position a score. It arrived in Stockfish 12 in 2020, and the old hand-written evaluation was removed completely in Stockfish 16.1 (February 2024).
UCI engine
Stockfish has no board of its own. It speaks the UCI protocol, so any chess program, website or app can ask it for moves and evaluations. That is how it plays on this page.
Open source
The code is public and free under the GPLv3 licence. It began in 2008 as a fork of Glaurung by Tord Romstad, Marco Costalba and Joona Kiiski, and is now developed by a worldwide community.
Tested on every change
Each change to the engine must prove itself in many thousands of test games on volunteers’ computers before it is accepted. Small gains add up from release to release.
Runs on anything
It plays at master strength on a phone and gets stronger with more cores and memory. The same engine is used on laptops, on servers and in engine championships.
Stockfish evolution
From the first release in 2008 to today's Stockfish 19
Stockfish 19 games with commentary
Play through each game on the board and read what the engine says about every move
Stockfish games collection
Curated from CCRL and TCEC top-engine matches
Stockfish vs the world's strongest engines
Browse Stockfish's complete archive against LCZero, Caissa, Berserk, Torch, Dragon, Obsidian and 40+ other top engines. Filter by opponent, opening, or sacrifice theme. Replay every game move-by-move, analyse with engine evaluation, or practise the winner's moves.
Browse the archiveStockfish vs top engines
Five of the most-played head-to-head archives
Stockfish compared with other engines
Side-by-side comparisons with real rating-list numbers and match results
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Stockfish 19 on YouTube
Games from our channels, explained move by move
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