An alpha-numerical identifier (digital fingerprint) that is unique to each electronic file. A hash value does not appear on the face of a document or file but is part of the file's metadata. MD5 and SHA are common types of hash values.

Documents with matching hash values are exact duplicates. Accordingly, counsel often use hash values to de-duplicate electronically stored information (ESI). However, hash values are susceptible to corruption during ESI collection. An ESI collector who is not skilled and careful may alter a file's hash value during collection and render de-duplication by hash value ineffective.

Counsel can produce hash values as either:

Because ESI produced as native files do not have Bates numbers stamped on the documents, counsel sometimes use hash values to identify each produced file.