Taking it off the air
On the “Settings” screen, under “Dangerous actions”, you can take the app off the air. The address stops immediately, the version is kept, and putting it back costs no new build.
Deleting
Deleting asks you to type the project name — a confirmation you cannot click by accident. The address stops answering immediately.
The code, the tables, the records and the users are kept by us and can be restored, but are no longer reachable from the system. If you want a copy of your own, export first.
An app taken off the air frees a slot in your plan's published-apps ceiling.