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Common utilities for parsing and handling peptide-spectrum matches and search engine results.

Project description

Common utilities for parsing and handling peptide-spectrum matches and search engine results in Python.

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psm_utils is a Python package with utilities for parsing and handling peptide-spectrum matches (PSMs) and proteomics search engine results. It is mainly developed to be used in Python packages developed at CompOmics, such as MS²PIP, DeepLC, and MS²Rescore, but can be useful to anyone dealing with PSMs and PSM files. Moreover, it provides an easy-to-use CLI and web server to convert search engine results from one PSM file format into another.

Goals and non-goals

  • To provide an easy-to-use Python API for handling PSMs.

  • To provide a unified Python API to the plethora of proteomics search engine output formats that are in existence.

  • To follow community standards: psm_utils pragmatically adheres to the standards developed by the HUPO Proteomics Standards Initiative, such as ProForma 2.0 , the Universal Spectrum Identifier, and mzIdentML

  • To be open and dynamic: psm_utils is fully open source, under the permissive Apache 2.0 license. New reader and writer modules can easily be added, and we welcome everyone to contribute to the project. See Contributing for more information.

  • NOT to reinvent the wheel: Instead, psm_utils heavily makes use of packages such as pyteomics and psims that have existing functionality for reading and/or writing PSM files. provides a unified, higher level Python API build on top of these packages.

Supported file formats

File format

psm_utils tag

Read support

Write support

OpenMS idXML


MaxQuant msms.txt


MS Amanda CSV




Peptide Record


Percolator tab






X!Tandem XML


Legend: ✅ Supported, ❌ Unsupported

psm_utils online

Open in streamlit

psm_utils online is a Streamlit-based web server built on top of the psm_utils Python package. It allows you to easily retrieve proteomics PSM statistics for any supported PSM file type, and to convert search engine results from one PSM file format into another. Click the badge above to get started!


Install with pip
pip install psm-utils
Install with Bioconda
conda install -c bioconda psm-utils

Full documentation

The full documentation, including a quickstart guide and Python API reference is available on


If you use psm_utils for your research, please cite the following publication:

psm_utils: A high-level Python API for parsing and handling peptide-spectrum-matches and proteomics search results.
Ralf Gabriels, Arthur Declercq, Robbin Bouwmeester, Sven Degroeve, Lennart Martens.
Journal of Proteome Research (2022). doi:10.1021/acs.jproteome.2c00609

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