You can search for entries in the OMA Browser using protein sequences. We provide two different search strategies, an exact search, which only reports entries in OMA that have an exact match with the query sequence, and an approximate search strategy that allows also for a few mismatches with the query sequence. The approximate search is highly optimized for speed and therefore faster than a BLAST search, but not as sensitive. It should mainly be used for retrieval of an entry, not for homology search.