CCleaner is a system-maintenance utility, not an antivirus — its job is clearing out accumulated junk, freeing disk space, and trimming startup overhead rather than blocking malware.
Junk File Cleanup
CCleaner scans for temporary files, browser cache, old log files, and leftover installer remnants that accumulate over months of normal use, then safely removes them to free up disk space.
Registry Cleaning
It scans the Windows registry for orphaned entries left behind by uninstalled programs and offers to remove them. The performance benefit of this specifically is modest on modern SSDs, though it's generally low-risk when using CCleaner's built-in backup-before-clean option.
Startup and Process Management
CCleaner's Startup tab shows every program configured to launch automatically at boot, letting you disable ones you don't need — a genuinely useful way to speed up boot time on a PC that's accumulated too many background auto-starting apps over time.
Is It Still Worth Using?
For freeing disk space and trimming startup bloat, yes — those remain genuinely useful, low-risk functions. The registry-cleaning benefit is smaller than it used to be on modern SSD-based systems, though it's not harmful when used as designed.