Stockfish 19 launched on September 5, 2026 with a gain of up to +44 ELO over Stockfish 18, winning more than three times as many game pairs as it lost in head-to-head testing. The gain comes from a new network architecture called SFNNv16. It remains free and open source under the GPLv3 license.
The unusual part is that it got smaller while getting stronger. SFNNv16 drops redundant threat features from the network and adds pawn-pair features instead — fewer inputs, better play. Our browser build went from 113MB to 99MB on the same upgrade.
We run Stockfish 19 across every tool on this site: the chess calculator, the game analyzer, and the AI bots. You can use it now, in your browser, with nothing to install.
The new architecture removes redundant threat features — which is what shrinks the binary — and introduces pawn-pair features, which is where the strength comes from. Most releases trade size for strength; this one improved both.
The small net is gone
Stockfish 16.1 added a secondary, faster network used in some positions. Stockfish 19 retires it completely, and play improves specifically in the positions where that small net used to underperform. One network, fewer surprises.
Universal binaries — no more guessing at instruction sets
Earlier releases made you choose between AVX2, AVX-512, BMI2 and friends, and choosing wrong meant either a crash or leaving performance on the table. Stockfish 19 detects your CPU at runtime and picks the optimal path itself. One download per platform.
New platforms: RISC-V, LoongArch, WebAssembly
Native support arrived for RISC-V (RVV) and LoongArch (LSX/LASX), along with 1GB Linux huge pages and WebAssembly build targets — the last of which is what makes running the real engine in a browser tab practical.
Stockfish 19 vs Stockfish 18
Stockfish 18
Stockfish 19
Released
January 31, 2026
September 5, 2026
Network
SFNNv10 (threat inputs)
SFNNv16 (pawn-pair features)
Secondary small net
Present (since 16.1)
Retired
Strength
Baseline
+44 ELO, >3:1 game pairs
CPU selection
Pick your own build
Universal, auto-detecting
Browser build size
113MB, split in 9 parts
99MB, single file
UCI_Elo range
1320 – 3190
1320 – 3190 (unchanged)
We measured it ourselves
We upgraded our own analysis servers from Stockfish 18 to 19 in September 2026, which meant running both on the same machine. Same hardware, one thread, 128MB hash, searching the starting position to depth 18:
Engine
Time to depth 18
Nodes
Eval
Stockfish 18
504ms
177,777
+0.49
Stockfish 19
307ms
112,909
+0.37
Stockfish 19 reached the same depth in about 40% less time while searching roughly 36% fewer nodes — it is pruning more aggressively rather than simply calculating faster. It also evaluates the starting position more conservatively (+0.37 against +0.49), which matches the wider pattern that stronger engines tend to rate the opening position closer to equal.
Stockfish 19 ELO Rating, and the Setting People Confuse It With
Two different numbers get mixed up constantly, so it is worth separating them.
Its actual playing strength. Stockfish 18 sits around 3650 on the CCRL standard rating list. Stockfish 19 tests roughly 44 ELO above that, which puts it further ahead of every human who has ever played — Magnus Carlsen's peak was 2882.
The UCI_Elo option. This tops out at 3190, and that is not a contradiction — it exists to make the engine play worse on purpose, and its ceiling was never meant to describe full strength. The range is 1320 to 3190 in both Stockfish 18 and 19, with the same interpolation between them, so settings carry over exactly.
Below 1320 there is nothing to set: every value clamps to the same floor and plays identically. Skill Level (0–20) does not help either, because it is ignored whenever UCI_LimitStrength is on. Convincing beginner-level play needs a different approach — which is why our bots below 1320 model the choice of move instead of asking the engine to play badly. The full skill level to ELO table has the exact numbers for every level.
Downloading Stockfish 19
The official release publishes eight native builds — Linux (x86-64, arm64, riscv64), Windows (x86-64, arm64), macOS universal, and Android (arm64, armv7) — each around 80MB, each auto-detecting your CPU.
One thing that catches people out: there is no .wasm file on the GitHub release, despite WebAssembly being listed among the new platform targets. That refers to the build system being able to target WebAssembly, not to a prebuilt browser binary. The browser build is published separately on npm as the stockfish package, which reached 19.0.0 on September 15, 2026 — ten days after the engine itself.
Or skip all of it. Our chess calculator already runs Stockfish 19 in the browser, and our game analyzer uses it for full-game reviews with plain-English explanations of where a game turned.
How to Use Stockfish 19 Free, Right Now
Open the chess calculator. The engine loads in your browser — nothing is installed and nothing is uploaded.
Set the position up: drag pieces on the board, paste a FEN, load a PGN, or scan a screenshot of a board from any site.
Analyse. You get the best move, the evaluation, and the alternative lines it considered.
To understand why, use the AI commentary — it explains the engine's choice in plain English rather than leaving you with a centipawn number.
If you want to practise against it instead of analysing with it, the bot ladder runs from 400 to 3650 ELO, and the ELO test estimates your own rating first so you can pick a level that is actually a fight.
Stockfish 19 FAQ
When was Stockfish 19 released?
September 5, 2026. It replaced Stockfish 18, which had held the top spot since January 31, 2026.
How much stronger is Stockfish 19 than Stockfish 18?
Up to 44 ELO points stronger in the Stockfish team's own testing, where it won more than three times as many game pairs as it lost against Stockfish 18.
What is the Stockfish 19 ELO rating?
Stockfish 18 sits around 3650 on the CCRL standard rating list, and Stockfish 19 tests roughly 44 ELO above it — so comfortably the strongest engine ever measured. Note this is different from the UCI_Elo setting, which only goes up to 3190; that option is for deliberately weakening the engine, not a measure of its real strength.
What is SFNNv16?
The 16th generation of Stockfish's NNUE network architecture. It removes redundant threat features, which makes the binary smaller, and adds new pawn-pair features, which makes it stronger. Fewer inputs and more strength at the same time.
What happened to the small neural network?
It was retired. Stockfish 16.1 introduced a secondary, faster net used in some positions; Stockfish 19 removes it entirely, which improves play in exactly the positions where that small net used to underperform.
Do I still need to pick between AVX2 and AVX-512?
No. Stockfish 19 ships universal binaries that detect your CPU's features at runtime and select the optimal code path, so there is one download per platform instead of a menu of instruction sets.
Which new platforms does Stockfish 19 support?
Native support was added for RISC-V (RVV) and LoongArch (LSX/LASX), plus 1GB Linux huge pages and WebAssembly build targets.
Can I use Stockfish 19 online for free?
Yes. ChessNextMove runs Stockfish 19 in your browser through WebAssembly. Open the chess calculator and analyse any position — no download, no installation, no account required.
Is there an official Stockfish 19 WebAssembly download?
Not on the GitHub release, which ships eight native builds for Linux, Windows, macOS and Android but no .wasm file. The browser build is published separately on npm as the 'stockfish' package, which reached version 19.0.0 on September 15, 2026.
What are the best Stockfish 19 analysis settings?
Set Hash to about half your free RAM, Threads to your physical core count, and search to depth 20-30 for serious analysis. To weaken it instead, enable UCI_LimitStrength and set UCI_Elo between 1320 and 3190, or use Skill Level 0-20 for coarser control.
Did the UCI_Elo range change in Stockfish 19?
No. It is still 1320 to 3190, identical to Stockfish 18, and the interpolation between those bounds is unchanged — so any UCI_Elo value you used before means the same thing now.
Is Stockfish 19 faster than Stockfish 18?
In our own testing on identical hardware, Stockfish 19 reached depth 18 from the starting position in 307ms against Stockfish 18's 504ms, using one thread and a 128MB hash on both.
Try Stockfish 19 in Your Browser
The strongest chess engine ever built, running in a browser tab. Analyze positions, review games, or challenge our AI bots.
