langdetect-rs

Port of Mimino666's langdetect which is Python-based port of Nakatani Shuyo's language-detection Java-based library. Even this README is mostly a copy of the Mimino666's one.

Language identification library for Rust.

W.I.P.

• Allow to add new languages
• Benchmarking in term of speed (via hyperfine?)
• Threadsafe API (do we need it though?)

Installation

Add to your Cargo.toml:

langdetect-rs = "*"

or run

cargo add langdetect-rs

Supported Rust Versions

Tested on Rust 1.91.0 (rustc 1.91.0 (f8297e351 2025-10-28))

Languages

langdetect-rs supports 55 languages out of the box (ISO 639-1 codes):

af, ar, bg, bn, ca, cs, cy, da, de, el, en, es, et, fa, fi, fr, gu, he,
hi, hr, hu, id, it, ja, kn, ko, lt, lv, mk, ml, mr, ne, nl, no, pa, pl,
pt, ro, ru, sk, sl, so, sq, sv, sw, ta, te, th, tl, tr, uk, ur, vi, zh-cn,
zh-tw

Example

You can run the included example:

cargo run --example simple

Example code (examples/simple/main.rs):

use langdetect_rs::detector_factory::DetectorFactory;

fn main() {
    let factory = DetectorFactory::default().build();

    // let mut detector = factory.create(None);
    match factory.detect("War doesn't show who's right, just who's left.", None) {
        Ok(lang) => println!("Detected language: {}", lang),
        Err(e) => println!("Detection error: {:?}", e),
    }

    // let mut detector = factory.create(None);
    match factory.detect("Ein, zwei, drei, vier", None) {
        Ok(lang) => println!("Detected language: {}", lang),
        Err(e) => println!("Detection error: {:?}", e),
    }

    match factory.get_probabilities("Otec matka syn.", None) {
        Ok(probs) => println!("Language probabilities: {:?}", probs),
        Err(e) => println!("Detection error: {:?}", e),
    }

    // For reproducibility use a fixed seed within explicitly defined detector
    let mut detector = factory.create(None);
    detector.seed = Some(42);
    detector.append("Otec matka syn.");
    match detector.get_probabilities() {
        Ok(probs) => println!("Language probabilities with seed: {:?}", probs),
        Err(e) => println!("Detection error: {:?}", e),
    }

    // Or you can set the seed for the factory itself and it will be inherited by detectors
    let factory_with_seed = DetectorFactory::default()
        .with_seed(Some(43))
        .build();
    match factory_with_seed.get_probabilities("Otec matka syn.", None) {
        Ok(probs) => println!("Language probabilities with seed: {:?}", probs),
        Err(e) => println!("Detection error: {:?}", e),
    }
}

NOTE

Language detection algorithm is non-deterministic, which means that if you try to run it on a text which is either too short or too ambiguous, you might get different results every time you run it.

To enforce consistent results, set the seed on the detector before detection:

let mut detector = factory.create(None);
detector.seed = Some(42); // Any u64 value
detector.append("your text");
println!("Detected language: {}", detector.detect());

How to Add a New Language?

This work in progress.

Initially I will take an idea from original Python library: https://github.com/Mimino666/langdetect?tab=readme-ov-file#how-to-add-new-language

And then I will try it to simplify the process.

Original project

Presentation of the language detection algorithm (on which original implementation is based): http://www.slideshare.net/shuyo/language-detection-library-for-java.