WebDAV

WebDAV (Web Distributed Authoring and Versioning), defined in RFC 4918, extends HTTP into a protocol for managing files and folders on a remote server. Where plain HTTP mostly reads and writes single resources, WebDAV adds the operations you need to treat a web server like a shared filesystem — creating collections, moving and copying resources, reading and writing metadata, and locking a file so two authors do not clobber each other’s edits.

• New HTTP methods - PROPFIND, PROPPATCH, MKCOL, COPY, MOVE, and LOCK/UNLOCK extend the familiar verb set.
• Properties - Arbitrary XML metadata can be attached to and queried from resources, separate from their content.
• Collections - First-class directory-like containers give the server a real namespace to organize resources.
• Locking - Shared and exclusive locks make collaborative authoring safe against overwrites.

In practice WebDAV shows up more as an infrastructure and content-management protocol than as a modern web API — it powers remote file mounts, calendaring and contacts extensions (CalDAV and CardDAV), and document-editing back ends. When I encounter it in an API estate, it is usually a mature, HTTP-native file surface rather than something teams are actively designing against today. It remains a clean example of how much you can layer onto HTTP’s method model without abandoning the protocol, which is exactly the instinct that later specs kept building on.