CCleaner — Veteran System Cleaning Tool, One Button to Freshen Up Your Computer
In a word: The most well-known system cleaning and optimization tool on Windows. One click to clear junk files, repair the registry, and manage startup items. While the free version is sufficient for daily use, be sure to download from official channels to avoid bundled software.
Do You Also Feel Your Computer Getting Slower Over Time?
Scenario 1: Your computer booted in 10 seconds when new. After a year, boot takes 1 minute. You open your C drive — it’s almost full, but you don’t know which files are safe to delete. Manually digging through AppData? Too tiring. You need a tool to “sweep for mines” with one click.
Scenario 2: You uninstalled a program, but its registry entries and residual folders remain in the system. Every boot, its update notification still pops up in the bottom right. You feel “incomplete uninstall” is worse than “not uninstalling.”
Scenario 3: Your browser cache has piled up to several GB. Typing in the address bar lags for ages. You know you can clear it in browser settings, but you’re not sure if clearing the cache will also delete your passwords and bookmarks. You don’t dare to click — so you keep enduring the increasingly slow browser.
CCleaner was born to solve these “junk accumulation” problems. It won’t make your computer 10x faster, but it can restore that “freshly installed system” feeling.
What Is CCleaner?
CCleaner (originally Crap Cleaner) is one of the oldest system cleaning tools on the Windows platform, developed by the British company Piriform (acquired by Avast in 2017). It does one simple thing: finds unnecessary junk files in your system and safely deletes them.
Its core positioning isn’t “system optimization” (those claiming to make your computer 10x faster are all scammers), but “clearing out unnecessary stuff” — after cleaning, you might find: several more GB on your C drive, a smoother browser, and slightly faster boot times.
CCleaner has had over 2.5 billion downloads worldwide, making it one of the most downloaded projects in SourceForge history. Although there have been some controversies since the Avast acquisition (more on that later), it’s still the most recognized name in system cleaning.
Core Features
1. One-Click Cleaning — The Most Used “Spring Cleaning” Feature
When you open CCleaner, it defaults to the “Cleaner” interface. Just click “Run Cleaner” and it automatically scans the following junk:
| Cleaning Category | Specific Content |
|---|---|
| Windows System Cache | Thumbnail cache, DNS cache, error reports, log files |
| Temporary Files | Windows Temp, User Temp, Recycle Bin |
| Browser Cache | Chrome/Firefox/Edge cache, cookies, history |
| Browser Data | Download history, session data, IndexedDB |
| Application Cache | Adobe Reader cache, Office cache, media player cache |
Real-world effect: First cleaning typically frees 2-10GB (depending on how long since your last clean). Subsequent regular cleanings free 500MB-2GB each time.
Safety Note: The items CCleaner checks by default are all safe and won’t delete your personal documents. If you’re unsure, you can click “View Files” after scanning before deciding to delete.
2. Registry Cleaning — Fixing Windows’ “Database Junk”
The Windows registry is a massive configuration database. Installing/uninstalling software leaves behind a lot of “invalid entries”:
- Residual registry entries from uninstalled software
- Incorrect file associations
- Startup items pointing to non-existent programs
- Invalid shared DLL references
CCleaner’s registry cleaning feature scans for these issues and automatically backs up the registry (restorable at any time) before cleaning. You won’t feel “faster” immediately after cleaning the registry, but it can reduce system errors — like those annoying “Cannot find xx.dll” pop-ups.
3. Tool Set — Not Just Cleaning, But Also Management
CCleaner includes a set of practical tools, hidden in the “Tools” menu on the left:
Startup Manager:
- View and manage programs that auto-start at boot
- Disable unnecessary startup items (QQ, Xunlei, Steam and other programs that quietly start in the background)
- Supports delayed startup (let certain programs start a while after boot)
Uninstaller:
- Cleaner than the system’s built-in “Add/Remove Programs”
- Automatically scans for residual files and registry entries after uninstallation
Duplicate File Finder:
- Find duplicate files by name, size, modification date
- Can filter scan scope (specific folders or full disk)
Disk Analyzer:
- Visual display of each folder’s space usage
- Quickly find “culprits” — folders taking up lots of space that you forgot about
System Restore Point Manager:
- View and manage Windows system restore points
- Delete old restore points to free up space
4. Browser Cleaning — Say Goodbye to “Cache Obesity”
CCleaner’s browser cleaning is more detailed than the browser’s built-in options:
- Supports Chrome, Firefox, Edge, Opera, Brave, Vivaldi, and other major browsers
- Can clean “cache” alone without touching “passwords/bookmarks” (what many users need most)
- Supports clearing browser autofill form data
- Supports clearing Flash cookies (though Flash is dead, residual data remains)
Professional Media and User Reviews
| Source | Review |
|---|---|
| CNET | ”CCleaner is the most popular system cleaner for Windows — it’s easy to use, effective, and the free version covers most needs” |
| TechRadar | ”CCleaner remains a powerful tool for freeing up disk space and keeping your system tidy, despite increasing competition from built-in Windows tools” |
| PCWorld | ”The registry cleaner and startup manager alone make CCleaner worth installing — just be careful to download it from the official site only” |
What Real Users Say
“I installed CCleaner on all 500+ computers at my company. For remote maintenance, 90% of ‘my computer is slow’ issues are solved by running CCleaner + disabling a few startup items remotely. Not because CCleaner is magic, but because most people’s computers are just too dirty.” — IT Operations Engineer, Zhihu
“CCleaner’s registry backup feature saved me once. I got carried away and cleaned everything possible in the registry. After reboot, WiFi wouldn’t connect. Luckily CCleaner had automatically backed up the registry. I restored it in safe mode and was fine. Lesson learned: always back up before cleaning the registry.” — Programmer, V2EX
“Been using CCleaner since version 3.x. Honestly, Windows 10/11’s built-in Disk Cleanup is much better than before — but CCleaner’s startup manager and browser cache cleaning are still better than the built-in ones. The uninstall feature in the Tools menu is also cleaner than the system’s built-in one.” — IT Manager, SegmentFault
Comparison with Similar Tools
| Dimension | CCleaner | BleachBit | Windows Disk Cleanup | Wise Disk Cleaner |
|---|---|---|---|---|
| Price | Free/Pro $29.95 | Completely Free | System Built-in Free | Free/Pro |
| One-Click Cleaning | ⭐⭐⭐⭐⭐ Most convenient | ⭐⭐⭐ Needs configuration | ⭐⭐⭐ Single function | ⭐⭐⭐⭐ Convenient |
| Registry Cleaning | Yes (auto backup) | Not supported | Not supported | Yes |
| Browser Cleaning | ⭐⭐⭐⭐⭐ Most detailed | ⭐⭐⭐⭐ Good | ⭐ Not supported | ⭐⭐⭐ Basic |
| Startup Manager | Built-in | None | Yes (Task Manager) | Built-in |
| Deep Cleaning Scope | ⭐⭐⭐⭐ Broad | ⭐⭐⭐⭐ Broad | ⭐⭐ Limited | ⭐⭐⭐ Moderate |
| Privacy Protection | ⭐⭐⭐ Average | ⭐⭐⭐⭐ Good | ⭐⭐ Basic | ⭐⭐⭐ Average |
| Open Source | No | Yes (GPL) | No | No |
| Interface Language | Chinese | Multi-language | System language | Chinese |
Selection advice:
- Most hassle-free, one-click cleaning → CCleaner (for beginners and experts alike)
- Completely free + open source → BleachBit (Linux users’ first choice, also has Windows version)
- Don’t want extra software → Windows Disk Cleanup (Win10/11’s built-in Disk Cleanup is actually sufficient)
Download and Installation Guide
Official Download
CCleaner’s official website is ccleaner.com:
| Channel | Download Address | Notes |
|---|---|---|
| Official Site (Recommended) | ccleaner.com | Windows, free and Pro versions |
| Microsoft Store | Search “CCleaner” in Microsoft Store | Microsoft Store version, auto-update |
Important Safety Note: After CCleaner was acquired by Avast, the installer includes bundled software by default (like Avast antivirus). During installation, be sure to choose “Custom Installation” and uncheck all bundled options:
- Download and run the installer
- Choose “Custom Installation” (don’t click “Quick Install”)
- Uncheck all bundled software options (Avast, browser extensions, etc.)
- Continue with installation, then close the auto-update popup
Additionally, in 2017, CCleaner suffered a supply chain attack (official installer was injected with malicious code, version 5.33). Although Avast fixed the issue and strengthened security measures, this incident reminds us: keep CCleaner updated, download from ccleaner.com, and never get it from third-party download sites.
Free vs Pro Version
| Feature | Free | Pro ($29.95/year) |
|---|---|---|
| One-Click Junk Cleaning | Yes | Yes |
| Registry Cleaning | Yes | Yes |
| Startup Manager | Yes | Yes |
| Real-Time Monitoring | No | Yes |
| Auto Update | No | Yes |
| Technical Support | No | Yes |
Recommendation: Free version is sufficient. Real-time monitoring isn’t very practical — you don’t need CCleaner running in the background constantly. Just manually open it and run a scan when needed.
FAQ
Q: Will CCleaner delete my files when cleaning junk? A: No. CCleaner cleans system temp files, caches, logs, and other “safe to delete” files. The items checked by default have been tested as safe. If you’re worried, click “View Files” before cleaning to inspect the specific contents.
Q: Is CCleaner’s registry cleaning safe? A: Relatively safe. CCleaner automatically creates a backup (.reg file) before cleaning the registry. If problems occur, you can double-click to restore. It’s recommended to confirm the backup file is created before each clean.
Q: Is CCleaner still worth installing in 2025? Isn’t Windows’ built-in tool enough? A: In 2025, Windows 10/11’s built-in “Disk Cleanup” and “Storage Sense” are indeed quite capable. CCleaner’s extra value lies in: (1) More detailed browser cache cleaning (2) Startup manager (3) Registry cleaning. If you find the built-in tools sufficient, you don’t need it. If you like the feeling of a “thorough clean,” CCleaner is still the best choice.
Q: I heard CCleaner has spyware issues? A: That was the 2017 supply chain attack (CCleaner 5.33), where the official installer was hacked and backdoors were added. Avast fixed the issue within days, and subsequent versions are safe. The latest CCleaner 6.x has no security issues. But if you’re still uneasy, you can use the open-source BleachBit instead.
CCleaner is the Swiss Army knife of the system cleaning world — it may not be the strongest in every function, but it’s the most convenient to have at hand. Startup manager, cache cleaning, registry repair… When your computer feels “off,” running CCleaner is the lowest-cost solution.