These are sometimes optional (pre-checked boxes), but many users click through.

If you are downloading CCleaner via a third-party aggregator like rsload:

RSLoad has been flagged by some security communities (like r/FREEMEDIAHECKYEAH ) for occasionally hosting files with unwanted bundled software or potential malware.

CCleaner excels at its primary function: clearing out temporary files, browser caches, system logs, and registry keys (though the latter is of debatable necessity in modern Windows). It recovers disk space quickly and safely, often finding gigabytes of data that the built-in Windows Disk Cleanup tool misses.