FEN

Generated by scripts/gen-format-pages.py from docs/data/format-metadata/, FILE_FORMATS.csv and docs/formats-master.csv. Do not edit by hand: change the source, then run the script.

FEN Preview.

At a glance

How much Poka reads

B4 Summary. The container and metadata are read and summarised (counts, properties, structure), but the main content is not rendered.

Confidence: medium (the reviewer read the code). Basis: Reviewed 2026-10-26: read parsers/poka-fen/src/main.rs (242 lines) and plugin.json. No unit tests or tests/samples.rs, and the corpus has no .fen sample. Covers .fen. The card counts positions, the side to move, standard starting positions, halfmove and fullmove ranges, castling masks, pieces and empty squares, and shows the first and last positions as FEN text, with comment and malformed lines. Judgement: B4: the positions are summarised but no board is drawn.

What Poka does not read

• No board is drawn for any position
• Only the first and last positions are shown, as text
• Legality (king count, side in check) is not checked

Libraries

Libraries Poka uses or has assessed for this format, with the status, licence and language the registry records.

• fenex (candidate; MIT; Rust; https://github.com/Smallsan/fenex) — Parses and writes FEN and algebraic notation, with legal move checks; v0.1.10 (Aug 2025). Early-stage crate.
• shakmaty (reference; GPL-3.0; Rust; https://github.com/niklasf/shakmaty) — copyleft; Mature chess rules library that reads and writes FEN, SAN and UCI. Copyleft (GPL-3.0 or later).
• fen (ucarion) (candidate; licence unconfirmed; Rust; https://lib.rs/crates/fen) — FEN parser with error handling; only release is 0.1.0 from 2015. Licence not shown on the lib.rs page.
• fenpix (candidate; MIT; Rust; https://github.com/Smallsan/fenpix) — Fenpix is a Rust library that converts FEN strings into pixel chess boards.; v0.2.4, updated 2024-03-11; matched on lib.rs, not tested

Sources

• parsers/poka-fen/src/main.rs
• parsers/poka-fen/plugin.json