208 Already Reported
Meaning
The members of a WebDAV binding have already been enumerated in a previous part of the response, and are not being included again.
When to Use
When a WebDAV request has multiple operations on the same resource (like a DAV binding), and you have already reported its status in a 207 Multi-Status response to avoid duplication.
Example
A DAV PROPFIND on a collection returns 207, and if a member was already reported, subsequent multi-status parts might use 208 Already Reported for that member.
When Not to Use
Do not use outside of WebDAV multi-status responses. If each resource’s status is unique, report them individually instead of using 208.
Source
RFC 5842 (WebDAV)