Stockfish 17.1 is the release immediately before the version currently bundled as the default. In practical terms it is indistinguishable from its successor for any human opponent — the differences between consecutive Stockfish releases are measured in a few dozen Elo, at a level far beyond what any player can perceive.
It is included because engine-versus-engine testing is one of the few contexts where those differences actually show up. Run it against Stockfish 18 across a series of games from a fixed opening and you can watch the newer version convert small advantages slightly more reliably.
Both a full and a Lite build are available. Lite uses a smaller neural network, which loads faster and uses less memory at some cost in strength.
What makes it distinctive
- ▸Near-identical playing strength to Stockfish 18 in human terms
- ▸Useful as a control when testing whether a difference is real
- ▸Available in full and Lite network sizes