What STOCKFISH does

Stockfish is a free, open-source chess engine originally forked from the Glaurung 2.1 engine in November 2008 by Marco Costalba, with Tord Romstad and Joona Kiiski joining the project shortly after. The engine combines classical alpha-beta Principal Variation Search with a proprietary NNUE (Efficiently Updatable Neural Network) evaluator — currently in its SFNNv10 iteration — alongside Syzygy endgame tablebase support, NUMA-aware memory optimization, and Correction History heuristics. It is distributed as native binaries for Windows, macOS, Linux, Android, and iOS via GitHub releases, the macOS and iOS App Stores, and the Homebrew package manager, and is embedded into a broad range of third-party chess GUIs and platforms.

Stockfish serves multiple constituencies: competitive and casual chess players, titled grandmasters seeking game preparation, chess platform operators integrating analysis into their products, and chess engine developers using it as a benchmark baseline. The product is validated externally through consistent dominance at the TCEC and CCC computer chess championships, and it underpins downstream services such as the ChessDB cloud database (45+ billion analyzed positions). The project operates as a community-driven open-source initiative under GPLv3, with no formal corporate entity, no institutional investors, and a small core of volunteer maintainers (Joost VandeVondele and Disservin as of 2026) supplemented by a global contributor base.

The business model is explicitly non-commercial: Stockfish generates no direct revenue, charges no licensing fees, and does not accept monetary donations. Development and testing are sustained through volunteer contributions and donated CPU time via the Fishtest distributed testing framework, with the most recent major release (Stockfish 18, January 31, 2026) advancing the engine's neural network architecture and search algorithms. The project has actively defended its GPLv3 license, notably through a 2021-2022 lawsuit and subsequent settlement with ChessBase GmbH over Fat Fritz 2 and Houdini 6.

Name

STOCKFISH

Legal name

Daylen Yang (Website copyright holder)

Website

https://stockfishchess.org

Company type

Private

Founded year

2008

Operating status

Operating

Headcount range

11–50 employees

Short description

Stockfish is a free, GPLv3-licensed open-source chess engine launched in 2008, combining alpha-beta search with NNUE neural network evaluation. It serves chess players, grandmasters, and third-party chess platforms worldwide, and generates no direct revenue.

Ownership category

akta.pro rank

GTM type

B2C

Offering type

Software

Cost components

Personnel, Technology or R&D, Infrastructure, Operations

Revenue model

1. Free/Open Source Distribution: Stockfish is completely free and open-source under GPLv3 license. The project does not generate direct revenue. It operates on volunteer contributions, community support, and donated computing resources through Fishtest. The project accepts CPU time donations for testing but does not accept monetary donations.

Pricing tiers

Go-to-market motion1 record

Distribution channels6 records

Marketing channels8 records

Core offering

Stockfish is a free, open-source, cross-platform chess engine written in C++ that combines alpha-beta (PVS) search with NNUE (Efficiently Updatable Neural Network) evaluation to provide world-class chess analysis and playing strength. The engine is distributed as command-line binaries for Windows, macOS, Linux, Android, and iOS, and is designed to be embedded in third-party chess GUIs and platforms. It is released under the GPLv3 license with no paid tiers or premium features.

Product overview

Stockfish is a single unified product: a free, open-source chess engine that operates as a command-line program. The engine is enhanced by the Fishtest distributed testing framework, which validates improvements through self-play games, and the nnue-pytorch trainer, which develops neural network evaluation models. The engine uses NNUE (Efficiently Updatable Neural Network) evaluation and alpha-beta search to provide chess analysis. It is available as downloadable binaries for Windows, macOS, Linux, Android, and iOS, and can be used with various third-party graphical user interfaces.

Differentiator

Problem solved

Functional benefit

Products and services

• Stockfish Chess Engine Free, open-source, cross-platform chess engine written in C++ combining alpha-beta (PVS) search with NNUE neural network evaluation. One of the strongest chess engines in the world, winner of TCEC and CCC championships, available for Windows, macOS, Linux, Android, and iOS, designed to be used within third-party chess GUIs.
• Fishtest Distributed Testing Framework Distributed testing framework for Stockfish development where volunteers contribute CPU time to run self-play games testing future engine versions. Uses SPRT (Sequential Probability Ratio Test) statistics to validate improvements, enabling rapid and rigorous validation of code changes across a globally distributed contributor base.
• nnue-pytorch Neural Network Trainer GPU-accelerated neural network trainer written in Python and C++ used for training Stockfish's NNUE (Efficiently Updatable Neural Network) evaluation networks on over 100 billion positions of Leela Chess Zero evaluation data.

Quantifiable outcome

• Wins 4x more game pairs than it loses against Stockfish 17
• +3 more outcomes

Named customers3 records

Segments3 records

Ideal customer profiles3 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Integration2 records

AI capability2 records

Feature9 records

Partnerships

Two partnerships are on record, tiered minor and core.

• ChessBase GmbHminorStrategic or Co-development Partner · 18 November 2022Legal settlement reached after Stockfish developers filed suit against ChessBase for GPLv3 license violations with Fat Fritz 2 and Houdini 6 products. ChessBase acknowledged Stockfish as the origin of key code, will no longer sell products containing Stockfish code, and will reinstate the license after one year. ChessBase created a Free Software Compliance Officer position and will credit Stockfish in future products.
• Leela Chess ZerocoreTechnology or IntegrationOngoing collaboration where Leela Chess Zero provides open data (evaluation data from their neural network training) essential for training Stockfish's NNUE networks. Leela Chess Zero is generally considered the strongest GPU-based chess engine. This partnership demonstrates the power of open-source collaboration, with both teams sharing data to improve their respective engines.

Scale indicators9 records

Recent moves6 records

Expansion highlights5 records

Broad incumbents

• Chess.com: Largest commercial online chess platform and organizer of the CCC Computer Chess Championship in which Stockfish competes. Broad incumbent that depends on Stockfish-class engines for its analysis features while controlling the premier competitive venue.
• Lichess: Free, open-source online chess platform that embeds Stockfish for server-side analysis. Comparable as a chess platform that ships Stockfish as the default engine to millions of players and as a fellow open-source community project.
• ChessBase GmbH: Largest commercial chess-software publisher (Fritz, Houdini, ChessBase reader/database). Broad incumbent that built closed-source products on top of Stockfish code, leading to the GPLv3 enforcement action; comparable as a chess-software ecosystem player.
• DeepMind (AlphaZero): Alphabet-owned AI lab whose AlphaZero famously defeated an earlier Stockfish build in 2017 and now publishes successor work such as Maia. Broad incumbent/research peer demonstrating the frontier-AI competitor Stockfish could face.

Emerging players

• Berserk: Open-source chess engine written in C with NNUE evaluation. Emerging/direct peer that explicitly forks/leverages the same NNUE paradigm popularized by Stockfish and competes in CCRL/CEGT rating lists.

Direct peers

• Komodo Chess Engine: Commercial chess engine from Don Dailey and Mark Lefler, also a TCEC/CCC competitor offering both a free and a paid 'Dragon' version. Direct product peer competing for the same engine-evaluation rankings and chess-platform integrations.
• Houdini (ChessBase): Chess engine formerly published by ChessBase that was the subject of Stockfish's GPLv3 lawsuit over Houdini 6. Direct peer in engine category and tournament circuit, though now commercially constrained by the 2022 settlement.
• Crafty Chess Engine: Long-established open-source chess engine by Robert Hyatt used in CCRL/CEGT rating measurement. Direct peer in the open-source chess-engine category with comparable distribution and tournament-circuit presence.
• Leela Chess Zero: Open-source chess engine using GPU-based deep neural networks; the principal technical rival to Stockfish and a data partner that supplies training positions. Closest direct peer in terms of open-source community model, engine category, and tournament competition (TCEC/CCC).
• GNU Chess: Long-running free/open-source chess engine under the GNU project. Direct peer sharing the open-source, command-line chess-engine product category, though with materially weaker competitive ratings.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks6 records

Key highlights6 records

Customer concentration

• Xx.com/stockfishchess
• GitHubgithub.com/official-stockfish/Stockfish
• LinkedInlinkedin.com/company/stockfish

Compliance1 record

Revenue estimate

Valuation estimate

Number of profiles

Profiles5 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about STOCKFISH