Engines are large. When you no longer need one, OPAL removes it safely — to the operating system’s recycle bin / trash, not a permanent delete — and cleans it out of the O3DE manifest.
Remove a single engine
Use the Remove action on an engine (available from the engine list and from an invalid-installation warning row). OPAL confirms, moves the engine directory to the OS trash, and unregisters it from the manifest.
Prune non-default engines
To reclaim space in one pass, use Prune. This bulk-removes every non-default engine, showing a confirmation modal first. As with single removal, pruned engines go to the OS trash rather than being erased outright, so a mistake is recoverable from your recycle bin.
What happens to pinned projects
If a project was pinned to an engine you remove, the project stays in your list but flags a missing-engine state. See Project status & health for how to reassign or reinstall.