The GI numbers are unique record identifiers that NCBI traditionally paired with accession numbers to designate records in the Nucleotide and Protein databases. Since the beginning of 2016, NCBI has been gradually transitioning to singular use of accession.version identifiers.

If you have a list of GIs that you want to update into accession.version identifiers, you can choose your method depending on the size of your list:

1. For a small number (<1000) of GIs:

• Access the Nucleotide or the Protein database on the web as needed for your set.
• Enter your GIs separated by commas in the search box and perform your search.
• You can download the records that you have obtained from the search (example):
  • Use the Send menu (top right above the results).
  • Select File and the Accession List format.
  • (If you choose other formats, you can currently opt for GIs to be included by check-marking the Show GI box.)

2. For up to a few thousand GIs:

• Use the NCBI E-utility EFetch.
• See the Converting GI Numbers to Accession.version blog for detailed instructions.

3. For large (>10,000) conversion tasks:

• Use the bulk conversion resource.
• See the Converting Lots of GI Numbers to Accession.version blog for detailed instructions.