CCleaner on Windows: How to Use It, What It Actually Does, and Safe Alternatives

CCleaner is the most popular Windows cleaning utility. But in recent years there have been security and usefulness concerns. Here's what you need to know before installing.

Is CCleaner Safe in 2026?

Short answer: free version is acceptably safe, but with caveats.

2017 — CCleaner was hacked and contained malware (fixed now)
Avast acquired CCleaner and added aggressive advertising
Installer tries to add Avast antivirus without clear consent

Bottom line: if you install it — carefully read each step and decline additional software. Built-in Windows alternatives exist for everything CCleaner does.

Install CCleaner

Download from ccleaner.com → "Free"
Uncheck any offers to install Avast or other software
Run as administrator

Clean Temporary Files

Launch CCleaner → "Custom Clean" → "Analyze" → "Run Cleaner"

Removes: Windows temp files, browser cache, Recycle Bin, Windows Update logs.

Uncheck "Cookies" to stay logged into websites.

Registry Cleaning — Should You?

Microsoft's official position: don't bother.

Registry "junk" has virtually no impact on modern Windows performance. Wrong registry deletion can break apps. Speed gains from registry cleaning are a myth.

Startup Manager

One of CCleaner's most useful features:

Tools → Startup → Windows

Same thing, free and safer:

Ctrl + Shift + Esc → Startup tab

Free Built-in Alternatives

Disk Cleanup

Win + R → cleanmgr → select C: → OK → "Clean up system files"

Storage Sense (automatic)

Win + I → System → Storage → Configure Storage Sense

BleachBit (open source, no ads)

Download from bleachbit.org

Summary

Feature	CCleaner	Built into Windows
Clean temp files	✅	✅ cleanmgr
Manage startup	✅	✅ Task Manager
Uninstall programs	✅	✅ Settings → Apps
Registry cleaning	✅ (not recommended)	❌
Ads and bundled software	⚠️	❌