Note: this post was last updated on July 26, 2016, a few outdated content has been updated to better reflect CCleaner's recent features and versions.
To download CCleaner (v5.20.5668 as of 19 Jul 2016), you can go to Piriform's official website or this CNET page.
Basic Feature – Clean Privacy
This function is the most frequently used one. It helps clear those footprints you left behind while running Windows or surfing the Internet. We can say it's a privacy cleaner. It can easily find those useless privacy files such as recently typed urls, cookies, history, caches, temporary files etc which you left behind when you are using browsers (IE, Firefox, Chrome) or running other Windows applications. Simply click "Analyze" to find out those useless stuff and "Run Cleaner" to get rid of them easily. Note: this feature can help free up lots of disk space in GBs.
CCleaner works for Windows operating sytems. If you use a Mac, see this Q&A for best register cleaner for Mac.
Basic Feature – Fix Registry
It's quite normal to encounter registry problems as long as you are using a Windows PC. Those problems may cause some unnecessary troubles (such as unable to open IE browser or certain applications). Registry problems like missing DLLs, unused file extensions, unused registry key, installers and so on. Just click "Scan for Issues" and get them fixed.
Advanced Feature – Extra Tools to Enhance PC
Right below the "Cleaner" and "Registry", there are 4 helpful "Tools". Have you ever tried them? Do not ignore them as you may regret, hah.
- Uninstall – You don’t have to go to Control Panel on Windows and uninstall programs unwanted. Instead, here you can easily remove them. Also you can Rename or Delete the Entries according to your preferences.
- Startup – Helps manage the auto-start programs when computer starts. If you want your PC to boot up more faster, disable those apps that you don’t often use.
- System Restore – Remove system restore points.
- Drive Wiper – as I wrote a post regarding free data file shredders, this Drive Wiper also one of the utilities that can be used to clean up disk completely. You may find it right in need when you want to donate a hard drive which contained your previous privacy or similar cases you want the information insides erased for good beyond recovery.
Advanced Feature – More Customized Options
In this area you have plenty of options to set up based on your preferences, such as keep some cookies you don't want CCleaner to delete, include or exclude files or folders to be emptied etc. One more tip: be aware of this "Secure Deletion" under "Settings". Usually I set it to "secure file deletion" even it is a little slower. I'll suggest you set it too, why? For your privacy security. When you select "normal file deletion", it's just another way to make those deleted files hidden as you may know it is quite possible to get them recovered with data recovery software (as many programs are capable of doing this). So set it to "secure deletion" and choose the passes you want. The more passes you select, the less likely to be recovered.
Pretty cool and powerful tool, I highly recommend.