CCleaner 5.0 running on Microsoft Windows
|Initial release||23 September 2003|
|Operating system||Windows XP and later,
Mac OS X Snow Leopard and later, Android 4.0.3 and later
|Platform||IA-32 and x64|
|Available in||47 languages|
CCleaner // (formerly Crap Cleaner), developed by Piriform, is a utility program used to clean potentially unwanted files (including temporary internet files, where malicious programs and code tend to reside) and invalid Windows Registry entries from a computer. CCleaner has been reviewed by Chip.de, TechRadar, PC Magazine and TechRepublic.
In September 2017, CCleaner v5.33 (32-bit Windows) was compromised with a backdoor in the software, enabling remote access of 2.27 million infected machines. On September 13, Piriform released CCleaner 5.34 and CCleaner Cloud 1.07.3191 that do not contain the malicious code.
CCleaner can delete temporary or potentially unwanted files left by certain programs, including Microsoft Edge, Internet Explorer, Firefox, Google Chrome, Opera, Safari, Windows Media Player, eMule, Google Toolbar, Netscape, Microsoft Office, Nero, Adobe Acrobat, McAfee, Adobe Flash Player, Sun Java, WinRAR, WinAce, WinZip and GIMP along with browsing history, cookies, recycle bin, memory dumps, file fragments, log files, system caches, application data, autocomplete form history, and various other data. The program also includes a registry cleaner to locate and correct problems in the Windows registry, such as missing references to shared DLLs, unused registration entries for file extensions, and missing references to application paths. CCleaner v2.27 and later can wipe the MFT free space of a drive, or the entire drive.
The License for the free version has common terms against reverse engineering, copying and sub-licensing, and it disclaims warranties and liability. The Business  and Professional licences have a 30-day warranty.
They "work closely" with Google Analytics and Google AdMob, "and may receive information about you from them..." "Information is retained on Content Delivery Networks", without any mention of deletion.
If the user provides an email address for their newsletter, subscription, or forums, they consider this personal information. "We may disclose your personal information to third parties if we are under a duty to disclose or share your personal data in order to comply with any legal obligation". This lets them contract with anyone to exchange personal information, since a contract puts them under a "legal obligation."
- "CCleaner v5.34". piriform.com. Piriform. 2017-09-12. Retrieved 2017-09-15.
- "CCleaner for Mac v1.14". piriform.com. Piriform. 2016-09-01. Retrieved 2017-02-24.
- "CCleaner - Android Apps". Google Play. 2017-08-22. Retrieved 2017-08-22.
- "What operating systems does CCleaner support?". CCleaner - FAQ. Piriform. Retrieved 5 November 2010.
- "Changing the language CCleaner uses". CCleaner Documentation. Piriform Ltd. Retrieved 28 October 2011.
- Archived CCleaner Website from 2004 showing the old name of Crap Cleaner
- "CCleaner - Optimization and Cleaning - Free Download". Ccleaner.com. Retrieved 26 October 2011.
- "CCleaner". chip.de. Retrieved February 21, 2016.
- "Download of the Day: CCleaner". techradar.com. Retrieved February 21, 2016.
- "CCleaner (for Mac) Review & Rating". pcmag.com. Retrieved February 21, 2016.
- "Five Tips For Using CCleaner To Degunk Your System". techrepublic.com. Retrieved February 21, 2016.
- Warren, Tom (18 September, 2017). "Hackers hid malware in CCleaner software". The Verge. Check date values in:
- "CCleaner - Features". Official web site. Piriform. Retrieved 3 June 2010.
- "Tuning Windows: Less Bull, More Speed". 20 May 2009. Retrieved 2 June 2009.
- "Screenshot #5: The Startup Tool". Official web site. Piriform. Retrieved 5 November 2010.
- "CCleaner Version History". Official web site. Piriform. 26 March 2013. Retrieved 26 March 2013.
- "Screenshot #6: The System Restore tool". Official web site. Piriform. Retrieved 5 November 2010.
- "CCleaner for Mac OS X". Ccleaner.com. Retrieved 25 December 2015.
- Ferri-Benedetti, Fabrizio (2014-04-18). "CCleaner for Android: too little, too late?". Softonic. Retrieved 2017-06-21.
- "Software License Agreement for users of CCleaner Free Software, undated". Piriform. Retrieved 2017-03-12.
- "Software License and Support Agreement for users of CCleaner Business Edition Software, undated". Piriform. Retrieved 2017-02-12.
- "Software License and Support Agreement for users of CCleaner Professional Software, undated". Piriform. Retrieved 2017-02-12.
- Rosenblatt, Seth (28 October 2010). "CCleaner". Download.com. CBS Interactive. Retrieved 15 May 2011.