syncthing-rest-api(7) on Linux
The text 8d821a452b0c, as Debian 12 (Bookworm) shipped it.
REST API Syncthing exposes a REST interface over HTTP on the GUI port. This is used by the GUI (from Javascript) and can be used by other processes wishing to control Syncthing. In most cases both the input and output data is in JSON format. The interface is subject to change.