The OMA Browser is a web-based interface to the data from the OMA project of the CBRG at the ETH Zürich. It offers a comprehensive search and numerous display options for 4.7 million proteins from 1000 species. The main features are the orthologous relationships which can be accessed either group-wise, where all group members are orthologous to all other group members, or on a sequence-centric basis, where for a given protein all its orthologs in all other species are displayed. An application note in Bioinformatics describes the main features of the OMA Browser:

A Schneider, C Dessimoz and GH Gonnet (2007): OMA Browser - Exploring Orthologous Relations across 352 Complete Genomes, Bioinformatics 23(16), pages 2180-2182. [Open Access]

Recent developments are described in 2011's Nucleic Acids Research Database Issue:

AM Altenhoff, A Schneider, GH Gonnet and C Dessimoz (2011): OMA 2011: orthology inference among 1000 complete genomes, Nucl. Acids Res., 2011, 39(suppl 1): D289-D294. [NAR: Open Access]

If you want to learn more about the underlying algorithm, we have prepared a webpage with details and further references.

The data displayed in the web interface is updated about twice a year. However, the OMA project itself is constantly increasing with new genomes being added or updated almost every day. For the latest developments of the project as well as for species trees or various statistics, we have a status page which displays the current status.

The following diagram provides an overview of the data flow in the OMA project:

The OMA Browser is developed and maintained by Adrian Altenhoff, Christophe Dessimoz and Adrian Schneider. For any questions, requests or comments, please contact or

The infrastructure used to run the OMA Browser is managed with the awesome cdist configuration management system.


Terms of Service
Our work (which include the OMA browser web site, the API and the predictions of orthology) is licensed under a Creative Commons Attribution-Share Alike 2.5 License.
Creative Commons License
The underlying sequences and annotations may be subject to third-party constraints. Users of the data are solely responsible for establishing the nature of and complying with any such intellectual property restrictions.