Corevoikko

Finnish natural language processing library -- spell checking, morphological analysis, hyphenation, grammar checking, and tokenization.

This is a Rust rewrite of the original Voikko C++ library, compiled to native code and WebAssembly. The original C++ source is preserved in libvoikko/legacy/ for reference.

Features

• Spell checking with compound word and derivation support
• Spelling suggestions tuned for common typing errors and OCR correction
• Morphological analysis with full inflection details
• Hyphenation with compound-aware splitting
• Grammar checking with context-sensitive paragraph analysis
• Tokenization and sentence splitting

Quick Start

npm (Browser / Node.js)

npm install @yongsk0066/voikko

import { Voikko } from '@yongsk0066/voikko';

// Node.js -- dictionary is bundled, zero config
const voikko = await Voikko.init();

// Browser -- WASM and dictionary fetched from CDN automatically
const voikko = await Voikko.init();

// Browser (self-hosted) -- serve files from your own server
const voikko = await Voikko.init('fi', { dictionaryUrl: '/dict/', wasmUrl: '/voikko.wasm' });

voikko.spell('koira');        // true
voikko.suggest('koirra');     // ['koira', ...]
voikko.analyze('koirien');    // [{ BASEFORM: 'koira', CLASS: 'nimisana', ... }]
voikko.hyphenate('kissa');    // 'kis-sa'
voikko.terminate();

Finnish dictionary files are bundled in the npm package. Node.js users need no additional setup. Browser users can rely on automatic CDN loading, or copy dictionary files from node_modules/@yongsk0066/voikko/dict/ to a public directory and pass dictionaryUrl.

Rust

cd libvoikko/rust
cargo test --all-features     # 637 tests
cargo clippy --all-features -- -D warnings

CLI Tools

Eight command-line tools for interactive use:

cd libvoikko/rust
VOIKKO_DICT_PATH=/path/to/dict cargo run -p voikko-cli --bin voikko-spell

Available: voikko-spell, voikko-suggest, voikko-analyze, voikko-hyphenate, voikko-tokenize, voikko-gc-pretty, voikko-baseform, voikko-readability.

Native Library (FFI)

cd libvoikko/rust
cargo build --release -p voikko-ffi
# produces target/release/libvoikko_ffi.{dylib,so,dll}

Bindings for Python (ctypes), Java (JNA), C# (P/Invoke), and Common Lisp (CFFI) are in libvoikko/python/, libvoikko/java/, libvoikko/cs/, libvoikko/cl/.

Finnish Dictionary

cd voikko-fi
make vvfst                    # requires foma, Python 3, GNU make
make vvfst-install DESTDIR=~/.voikko

How It Fits Together

flowchart LR
    dict[voikko-fi dict] --> core[voikko-core + fst + fi]
    core --> wasm[voikko-wasm]
    core --> ffi[voikko-ffi]
    core --> cli[voikko-cli]
    wasm --> js[JS/TS npm]
    ffi --> py[Python]
    ffi --> java[Java]
    ffi --> cs[C#]
    ffi --> cl[Common Lisp]

The Rust workspace in libvoikko/rust/ contains six crates. The Finnish language module (voikko-fi) implements all NLP logic on top of shared types (voikko-core) and the FST engine (voikko-fst). Two output crates expose this to other languages: voikko-wasm for JavaScript via WebAssembly, and voikko-ffi for native bindings through a C API. The voikko-cli crate provides standalone command-line tools.

Language Bindings

License

The repository uses layered licensing:

• Repository overall: GPL 3+
• libvoikko: additionally available under MPL 1.1 / GPL 2+ / LGPL 2.1+ (tri-license)
• data, voikko-fi: additionally available under GPL 2+

See LICENSE and libvoikko/LICENSE.CORE for full details.

Credits

This project is a Rust rewrite of Voikko, originally created by Harri Pitkanen and contributors. The linguistic data in voikko-fi/ is the work of the Voikko project contributors.

Rust rewrite and npm package by Yongseok Jang.

Documentation

• LEARNING.md — domain knowledge guide for newcomers (FST, Finnish morphology, spell checking concepts, with AI study prompts)
• ARCHITECTURE.md — Rust codebase architecture and design decisions

Links

• Live Demo — try all features in the browser, no install needed
• npm package
• Original Voikko project