Montreal Forced Aligner

The Montreal Forced Aligner is a command line utility for performing forced alignment of speech datasets using Kaldi (http://kaldi-asr.org/).

Please see the documentation http://montreal-forced-aligner.readthedocs.io for installation and usage.

If you run into any issues, please check the mailing list for fixes/workarounds or to post a new issue.

Citation

MFA 3.0

For citing the latest version of MFA and its pretrained models, please use:

McAuliffe, Michael, Kaylynn Gunter, Michael Wagner, and Morgan Sonderegger (2026). Montreal Forced Aligner and the state of speech-to-text alignment in 2026. In Proceedings of Interspeech 2026.

@inproceedings{mcauliffe26_interspeech,
 author={McAuliffe, Michael and Gunter, Kaylynn and Wagner, Michael and Sonderegger, Morgan},
 title={{Montreal Forced Aligner and the state of speech-to-text alignment in 2026}},
 year=2026,
 booktitle={Proc. Interspeech 2026}
}

MFA 1.0

For citing the original software and models (upgrading to the MFA 3.X is recommended!), please use:

McAuliffe, Michael, Michaela Socolof, Sarah Mihuc, Michael Wagner, and Morgan Sonderegger (2017). Montreal Forced Aligner: trainable text-speech alignment using Kaldi. In Proceedings of Interspeech 2017.

@inproceedings{mcauliffe17_interspeech,
 author={McAuliffe, Michael and Socolof, Michaela and Mihuc, Sarah and Wagner, Michael and Sonderegger, Morgan},
 title={{Montreal Forced Aligner: Trainable Text-Speech Alignment Using Kaldi}},
 year=2017,
 booktitle={Proc. Interspeech 2017},
 pages={498--502},
 doi={10.21437/Interspeech.2017-1386}
}

Installation

You can install MFA either entirely through conda or a mix of conda for Kaldi and Pynini dependencies and Python packaging for MFA itself

Conda installation

MFA is hosted on conda-forge and can be installed via:

conda install -c conda-forge montreal-forced-aligner

in your environment of choice.

Source installation

If you'd like to install a local version of MFA or want to use the development set up, the easiest way is first create the dev environment from the yaml in the repo root directory:

conda env create -n mfa-dev -f environment.yml

Alternatively, the dependencies can be installed via:

conda install -c conda-forge python=3.11 kaldi librosa praatio tqdm requests colorama pyyaml pynini openfst baumwelch ngram

MFA can be installed in develop mode via:

pip install -e .[dev]

You should be able to see appropriate output from mfa version

Development

The test suite is run via tox -e py38-win or tox -e py38-unix depending on the OS, and the docs are generated via tox -e docs

Quick links

• Getting started docs
• User Guide
• API Reference
• Release notes
• MFA Models
• Eleanor Chodroff's MFA tutorial
• @mmcauliffe's forced alignment blog posts