Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Efficient Javascript implementation of Levenshtein algorithm with asynchronous callback support
Branch: master


latest commit 321ca56691
@hiddentao authored

fast-levenshtein - Levenshtein algorithm in Javascript

Build Status

An efficient Javascript implementation of the Levenshtein algorithm with asynchronous callback support.


  • Works in node.js and in the browser.
  • Better performance than other implementations by not needing to store the whole matrix (more info).
  • Provides synchronous and asynchronous versions of the algorithm.
  • Asynchronous version is almost as fast as the synchronous version for small strings and can also provide progress updates.
  • Comprehensive test suite and performance benchmark.
  • Small: <1 KB minified and gzipped



Install using npm:

$ npm install fast-levenshtein


Using bower:

$ bower install fast-levenshtein

If you are not using any module loader system then the API will then be accessible via the window.Levenshtein object.



var levenshtein = require('fast-levenshtein');

var distance = levenshtein.get('back', 'book');   // 2
var distance = levenshtein.get('我愛你', '我叫你');   // 1


var levenshtein = require('fast-levenshtein');

levenshtein.getAsync('back', 'book', function (err, distance) {
  // err is null unless an error was thrown
  // distance equals 2

Asynchronous with progress updates

var levenshtein = require('fast-levenshtein');

var hugeText1 = fs.readFileSync(...);
var hugeText2 = fs.readFileSync(...);

levenshtein.getAsync(hugeText1, hugeText2, function (err, distance) {
  // process the results as normal
}, {
  progress: function(percentComplete) {
    console.log(percentComplete + ' % completed so far...');

Building and Testing

To build the code and run the tests:

$ npm install -g grunt-cli
$ npm install
$ npm run build


Thanks to Titus Wormer for encouraging me to do this.

Benchmarked against other node.js levenshtein distance modules (on Macbook Air 2012, Core i7, 8GB RAM):

Running suite Implementation comparison [benchmark/speed.js]...
>> levenshtein-edit-distance x 234 ops/sec ±3.02% (73 runs sampled)
>> levenshtein-component x 422 ops/sec ±4.38% (83 runs sampled)
>> levenshtein-deltas x 283 ops/sec ±3.83% (78 runs sampled)
>> natural x 255 ops/sec ±0.76% (88 runs sampled)
>> levenshtein x 180 ops/sec ±3.55% (86 runs sampled)
>> fast-levenshtein x 1,792 ops/sec ±2.72% (95 runs sampled)
Benchmark done.
Fastest test is fast-levenshtein at 4.2x faster than levenshtein-component

You can run this benchmark yourself by doing:

$ npm install -g grunt-cli
$ npm install
$ npm run build
$ npm run benchmark


If you wish to submit a pull request please update and/or create new tests for any changes you make and ensure the grunt build passes.

See for details.


MIT - see

Something went wrong with that request. Please try again.