HTTP 102 – Processing
The server has received and is processing the request, but no response is available yet (WebDAV).
Common use case
Used by slow WebDAV operations (like copying a large collection of files) to keep the connection alive and stop the client from timing out while it waits.
Example
HTTP/1.1 102 Processing
History
Defined in RFC 2518 (1999) for WebDAV, later refined in RFC 4918 (2007).
Deprecated / legacy status
Not formally deprecated, but RFC 7231 recommends against relying on it because most HTTP/1.1 clients built before its introduction do not understand interim responses and may misbehave.