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Library for fast text representation and classification.

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fastText is a library for efficient learning of word representations and sentence classification.


Table of contents



Supplementary data


You can find answers to frequently asked questions on our website.


We also provide a cheatsheet full of useful one-liners.


We are continuously building and testing our library, CLI and Python bindings under various docker images using circleci.

Generally, fastText builds on modern Mac OS and Linux distributions. Since it uses some C++11 features, it requires a compiler with good C++11 support. These include :

  • (g++-4.7.2 or newer) or (clang-3.3 or newer)

Compilation is carried out using a Makefile, so you will need to have a working make. If you want to use cmake you need at least version 2.8.9.

One of the oldest distributions we successfully built and tested the CLI under is Debian jessie.

For the word-similarity evaluation script you will need:

  • Python 2.6 or newer
  • NumPy & SciPy

For the python bindings (see the subdirectory python) you will need:

  • Python version 2.7 or >=3.4
  • NumPy & SciPy
  • pybind11

One of the oldest distributions we successfully built and tested the Python bindings under is Debian jessie.

If these requirements make it impossible for you to use fastText, please open an issue and we will try to accommodate you.

Building fastText

We discuss building the latest stable version of fastText.

Getting the source code

You can find our latest stable release in the usual place.

There is also the master branch that contains all of our most recent work, but comes along with all the usual caveats of an unstable branch. You might want to use this if you are a developer or power-user.

Building fastText using make (preferred)

$ wget
$ unzip
$ cd fastText-0.9.2
$ make

This will produce object files for all the classes as well as the main binary

. If you do not plan on using the default system-wide compiler, update the two macros defined at the beginning of the Makefile (CC and INCLUDES).

Building fastText using cmake

For now this is not part of a release, so you will need to clone the master branch.

$ git clone
$ cd fastText
$ mkdir build && cd build && cmake ..
$ make && make install

This will create the fasttext binary and also all relevant libraries (shared, static, PIC).

Building fastText for Python

For now this is not part of a release, so you will need to clone the master branch.

$ git clone
$ cd fastText
$ pip install .

For further information and introduction see python/

Example use cases

This library has two main use cases: word representation learning and text classification. These were described in the two papers 1 and 2.

Word representation learning

In order to learn word vectors, as described in 1, do:

$ ./fasttext skipgram -input data.txt -output model


is a training file containing
encoded text. By default the word vectors will take into account character n-grams from 3 to 6 characters. At the end of optimization the program will save two files:
is a text file containing the word vectors, one per line.
is a binary file containing the parameters of the model along with the dictionary and all hyper parameters. The binary file can be used later to compute word vectors or to restart the optimization.

Obtaining word vectors for out-of-vocabulary words

The previously trained model can be used to compute word vectors for out-of-vocabulary words. Provided you have a text file

containing words for which you want to compute vectors, use the following command:
$ ./fasttext print-word-vectors model.bin < queries.txt

This will output word vectors to the standard output, one vector per line. This can also be used with pipes:

$ cat queries.txt | ./fasttext print-word-vectors model.bin

See the provided scripts for an example. For instance, running:

$ ./

will compile the code, download data, compute word vectors and evaluate them on the rare words similarity dataset RW [Thang et al. 2013].

Text classification

This library can also be used to train supervised text classifiers, for instance for sentiment analysis. In order to train a text classifier using the method described in 2, use:

$ ./fasttext supervised -input train.txt -output model


is a text file containing a training sentence per line along with the labels. By default, we assume that labels are words that are prefixed by the string
. This will output two files:
. Once the model was trained, you can evaluate it by computing the precision and recall at k ([email protected] and [email protected]) on a test set using:
$ ./fasttext test model.bin test.txt k

The argument

is optional, and is equal to
by default.

In order to obtain the k most likely labels for a piece of text, use:

$ ./fasttext predict model.bin test.txt k

or use

to also get the probability for each label
$ ./fasttext predict-prob model.bin test.txt k


contains a piece of text to classify per line. Doing so will print to the standard output the k most likely labels for each line. The argument
is optional, and equal to
by default. See
for an example use case. In order to reproduce results from the paper 2, run
, this will download all the datasets and reproduce the results from Table 1.

If you want to compute vector representations of sentences or paragraphs, please use:

$ ./fasttext print-sentence-vectors model.bin < text.txt

This assumes that the

file contains the paragraphs that you want to get vectors for. The program will output one vector representation per line in the file.

You can also quantize a supervised model to reduce its memory usage with the following command:

$ ./fasttext quantize -output model

This will create a

file with a smaller memory footprint. All the standard functionality, like
work the same way on the quantized models:
$ ./fasttext test model.ftz test.txt
The quantization procedure follows the steps described in 3. You can run the script
for an example.

Full documentation

Invoke a command without arguments to list available arguments and their default values:

$ ./fasttext supervised
Empty input or output path.

The following arguments are mandatory: -input training file path -output output file path

The following arguments are optional: -verbose verbosity level [2]

The following arguments for the dictionary are optional: -minCount minimal number of word occurrences [1] -minCountLabel minimal number of label occurrences [0] -wordNgrams max length of word ngram [1] -bucket number of buckets [2000000] -minn min length of char ngram [0] -maxn max length of char ngram [0] -t sampling threshold [0.0001] -label labels prefix [label]

The following arguments for training are optional: -lr learning rate [0.1] -lrUpdateRate change the rate of updates for the learning rate [100] -dim size of word vectors [100] -ws size of the context window [5] -epoch number of epochs [5] -neg number of negatives sampled [5] -loss loss function {ns, hs, softmax} [softmax] -thread number of threads [12] -pretrainedVectors pretrained word vectors for supervised learning [] -saveOutput whether output params should be saved [0]

The following arguments for quantization are optional: -cutoff number of words and ngrams to retain [0] -retrain finetune embeddings if a cutoff is applied [0] -qnorm quantizing the norm separately [0] -qout quantizing the classifier [0] -dsub size of each sub-vector [2]

Defaults may vary by mode. (Word-representation modes

use a default
of 5.)


Please cite 1 if using this code for learning word representations or 2 if using for text classification.

Enriching Word Vectors with Subword Information

[1] P. Bojanowski*, E. Grave*, A. Joulin, T. Mikolov, Enriching Word Vectors with Subword Information

  title={Enriching Word Vectors with Subword Information},
  author={Bojanowski, Piotr and Grave, Edouard and Joulin, Armand and Mikolov, Tomas},
  journal={Transactions of the Association for Computational Linguistics},

Bag of Tricks for Efficient Text Classification

[2] A. Joulin, E. Grave, P. Bojanowski, T. Mikolov, Bag of Tricks for Efficient Text Classification

  title={Bag of Tricks for Efficient Text Classification},
  author={Joulin, Armand and Grave, Edouard and Bojanowski, Piotr and Mikolov, Tomas},
  booktitle={Proceedings of the 15th Conference of the European Chapter of the Association for Computational Linguistics: Volume 2, Short Papers},
  publisher={Association for Computational Linguistics},
} Compressing text classification models

[3] A. Joulin, E. Grave, P. Bojanowski, M. Douze, H. Jégou, T. Mikolov, Compressing text classification models

  title={ Compressing text classification models},
  author={Joulin, Armand and Grave, Edouard and Bojanowski, Piotr and Douze, Matthijs and J{\'e}gou, H{\'e}rve and Mikolov, Tomas},
  journal={arXiv preprint arXiv:1612.03651},

(* These authors contributed equally.)

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