A tiddler can be created or updated over HTTP by using the HTTP API to access /bags/{bag_name}/tiddlers/{tiddler_title} and sending a PUT request containing a JSON tiddler. The content-type header must be set to application/json.

For a tiddler that already exists in the store, to make edits the current user must pass the edit constraint on the bag. To create a new tiddler, the current user must pass the create constraint.

See How can I use curl to create stuff in TiddlyWeb? for a simple example.