arangodb/Documentation/Books/Users/NamingConventions/DocumentKeys.md

Document Keys

Users can define their own keys for documents they save. The document key will be saved along with a document in the _key attribute. Users can pick key values as required, provided that the values conform to the following restrictions:

• The key must be at least 1 byte and at most 254 bytes long. Empty keys are disallowed when specified (though it may be valid to completely omit the _key attribute from a document)
• It must consist of the letters a-z (lower or upper case), the digits 0-9, the underscore (_), dash (-), or colon (:) characters only
  • Any other characters, especially multi-byte sequences, whitespace or punctuation characters cannot be used inside key values
• The key must be unique within the collection it is used

Keys are case-sensitive, i.e. myKey and MyKEY are considered to be different keys.

Specifying a document key is optional when creating new documents. If no document key is specified by the user, ArangoDB will create the document key itself as each document is required to have a key.

There are no guarantees about the format and pattern of auto-generated document keys other than the above restrictions. Clients should therefore treat auto-generated document keys as opaque values and not rely on their format.