Open any Unreal Engine 5.8 project and 173 engine plugins are enabled by default. They appear nowhere in your .uproject, so no diff ever showed them to a reviewer - and every one of them is loading in your editor right now.

The manual answer is the one the UE forums keep recording: turn plugins off one at a time and see what breaks. A real user doing exactly that disabled critical engine plugins and broke their project. That failure is the reason this tool exists, and the reason it is built the way it is.

It never says "unused." That word is a lie no static tool can back. Plugin Cleaner reads six evidence channels and sorts every enabled plugin into three buckets, not two:

REFERENCED - the row shows the referencing asset, file and line. You are never asked to trust a bare verdict.
NO REFERENCE FOUND - every channel came back clean. That is a statement about what the scan could see, not a claim about your project. It is the only bucket the disable action will ever act on, and only after you have seen the diff.
UNDECIDABLE - no honest verdict is available (string-constructed loads, or no readable reference channel). Always kept. Never acted on.

The six channels: asset-registry package dependencies; /Script/ module dependencies (a Blueprint using a C++ class from a code-only plugin - the most common real reference, and one a content-only scan structurally cannot see); Build.cs dependency lists; Config/*.ini class paths (how a renderer or input setting silently binds a plugin with no asset and no code reference anywhere); and plugin-to-plugin dependencies resolved to a fixpoint.

Everything the scan cannot read pushes a plugin toward KEEP, and every unreadable channel is printed in the report rather than silently dropped.

https://csaf.itch.io/plugin-cleaner - $14.99, Unreal Engine 5.8.

This tool is AI-authored and labelled as such on its store page.