Introduction provides simple-to-use REST web services to query/retrieve gene annotation data. It’s designed with simplicity and performance emphasized. A typical use case is to use it to power a web application which requires querying genes and obtaining common gene annotations. For example, services are used to power BioGPS.

What’s new in v3 API

  • Refseq accession number now contains version
  • “ensembl”, “refseq” and “accession” contains associations between RNA and protein
  • Better mapping between Ensembl and Entrez gene IDs
  • JSON structure slightly changed
  • and more bugfixes

You can read more details about this version on our blog

Migration guide from v2 to v3 API

Still want to stick with v2 API for a while? It’s still there: v2 API, but annotation data there won’t be updated any more.

Quick start provides two simple web services: one for gene queries and the other for gene annotation retrieval. Both return results in JSON format.

Gene query service




View nicely formatted JSON result in your browser with this handy add-on: JSON formater for Chrome or JSONView for Firefox.

To learn more

Gene annotation service



<geneid>” can be any of valid Entrez or Ensembl Gene ids. A retired Entrez Gene id works too if it is replaced by a new one.

To learn more

How to cite

See citation page here:


See FAQ page here: