A PC that lags on startup, security alerts ignored for months, a browser cluttered with temporary files: we all know this scenario. Avast and CCleaner consistently appear in recommendations to address these issues, but these two programs do not cover the same needs at all. One protects against digital threats, while the other cleans the system to restore its smoothness. Understanding this distinction prevents the installation of one thinking it replaces the other.
Privacy and recent vulnerabilities: what has changed since 2023
Before comparing the features, we must discuss what most comparisons gloss over: the security incidents that have affected both software in recent years. These events directly impact the trust we can place in them.
On the Avast side, the U.S. Federal Trade Commission issued a ruling in February 2024. The agency concluded that Avast had misled its users about the privacy of their browsing data. The result: a fine of $16.5 million and a ban on selling or licensing browsing data for advertising purposes. This is no longer just a media controversy related to the Jumpshot case; it is a formal regulatory obligation.
On the CCleaner side, a global attack exploiting a vulnerability in the MOVEit transfer tool exposed the data of some paying customers in 2023. Gen Digital, the parent company, confirmed the incident. For those who want to learn everything about Avast and CCleaner, these episodes remind us that even protection and optimization tools are not immune to vulnerabilities.
These two cases do not disqualify the software, but they require checking data collection settings after each installation. On Avast, disable data sharing in the privacy settings. On CCleaner, limit permissions to strict system cleaning.
Avast as antivirus: lab results and daily protection
Avast remains a high-performing free antivirus, and this is not just a subjective impression. In the AV-TEST tests of August 2026, Avast received the highest score in all three categories: protection, performance, and usability. This score places the free version on par with several paid solutions.
In daily use, real-time protection covers downloaded files, email attachments, and web browsing. The web shield blocks phishing attempts before the page fully loads. The premium version adds a configurable firewall and webcam protection.
What Avast does not do
Avast does not clean temporary files accumulated by the system or browsers. It does not manage programs launched at startup, nor does it fix Windows registry errors. Avast Cleanup Premium exists, but it is a separate paid module, distinct from the basic antivirus. The antivirus protects against threats; it does not optimize system performance.
CCleaner for system optimization: targeted cleaning and startup management
CCleaner steps in where Avast stops. When the PC takes two minutes to start up or the hard drive shows an abnormal fill rate, it is generally an accumulation issue, not a virus.
The software targets several sources of clutter:
- The temporary files from the system and browsers, which can represent several gigabytes on a machine used for a year or two without cleaning
- The startup programs, many of which have silently added themselves over installations, extending boot time
- Obsolete Windows registry entries left by uninstalled software, which can cause minor errors
The free version covers most of these functions. The Pro version adds real-time monitoring and automatic updates for third-party software installed on the PC.
The concrete limits of CCleaner
CCleaner does not detect any viruses, malware, or ransomware. It does not block phishing sites, nor does it monitor network connections. Using CCleaner without antivirus is like cleaning a house with the door left open. The system will be clean, but not protected.
Feedback varies on the actual usefulness of registry cleaning: on recent machines with SSDs, the performance gain is often imperceptible. However, on an older computer with a mechanical hard drive, cleaning temporary files frees up space that translates to measurable responsiveness.
Using Avast and CCleaner together: on-the-ground setup
You install both when you want to cover both security and system maintenance without going through an all-in-one paid suite. The combination works, provided you follow a few settings.
- Install Avast first, then CCleaner. The antivirus must be active before any cleaning operation to prevent a malicious file from slipping through during installation
- Disable promotional notifications from both software in their respective settings, or risk receiving pop-ups every hour
- Exclude the Avast folder in CCleaner’s cleaning settings, to avoid accidentally deleting quarantine or virus signature files
- Schedule CCleaner cleaning once a week, not daily, as too frequent cleaning can remove caches useful to browsers
Avast manages real-time protection, while CCleaner intervenes occasionally for maintenance. The two do not conflict if each stays within its scope. The problem arises when Avast Cleanup Premium is activated alongside CCleaner: both optimization tools may then target the same files and cause unpredictable behavior.
For machines running Windows 11, the system already includes basic disk cleaning and Microsoft Defender as antivirus. The combination of Avast plus CCleaner remains relevant if you seek more aggressive virus detection than Defender and more granular cleaning than the built-in tool. On a recent PC with few installed programs, the native Windows tools are often sufficient and the addition of third-party software becomes optional.
