This comprehensive analysis examines the critical question of which antivirus solutions and security tools can effectively work alongside Avast, a widely-used antivirus platform protecting 435 million devices globally. The research reveals a nuanced landscape in which traditional full antivirus programs should never be combined with Avast, but rather specific on-demand scanning tools, malware removal utilities, and supplementary security features can coexist harmoniously with Avast to create a layered security architecture. This report synthesizes extensive technical evidence, user experiences, and independent security testing data to provide a definitive guide on compatible security software, addressing a common misconception that adding multiple antivirus programs enhances protection rather than degrading system performance and security efficacy.
The Fundamental Problem: Why Multiple Antivirus Programs Cannot Coexist
The question of running multiple antivirus programs simultaneously represents one of the most misunderstood aspects of computer security. Many users logically assume that combining multiple antivirus solutions would provide better protection, following the intuitive reasoning that if one scanner misses a threat, another might catch it. This assumption, while superficially reasonable, fundamentally misunderstands how antivirus programs interact with Windows operating systems and with each other. The technical architecture of Windows was originally designed to support only a single antivirus engine at the system level, creating inherent conflicts when multiple programs attempt to perform identical protective functions simultaneously.
When two full antivirus programs are installed and running on the same Windows system, they immediately begin competing for the same system resources and attempting to intercept the same file operations. Both programs want to scan files as they are accessed, downloaded, or written to disk, but the Windows antivirus application programming interface (API) is fundamentally not designed to accommodate this dual registration. Experimentation and documented user experiences reveal the concrete consequences of this architectural incompatibility. Users who installed Avast alongside Norton reported terribly slow computer performance. Those who combined Avast with Kaspersky experienced not only severe slowdowns but also application crashes, particularly affecting browsers like Firefox, Internet Explorer, and Chrome. When Avast was combined with Avira, the conflicts emerged most dramatically when viruses were detected, as both programs attempted to handle the threat simultaneously, causing the system to malfunction. Perhaps most catastrophically, one user reported that combining Avast with NOD32 caused system hang-ups immediately after login, requiring a restart to restore any functionality.
These are not mere theoretical concerns or marginal performance degradations. When multiple antivirus programs detect the same threat, they both attempt to execute their own removal procedures and quarantine actions simultaneously. Picture this scenario: one program successfully identifies and quarantines a malicious file, moving it to a protected folder. Meanwhile, the second antivirus program also identifies the same threat and attempts its own removal procedure, only to find that the file has already been moved or locked by the first program. This conflict can result in system instability, cascading errors, and in severe cases, the endless loop phenomenon where competing programs continually copy files back and forth as each one detects the other’s scanning activities. The system literally exhausts its memory resources as the two programs battle for control, typically resulting in a complete system freeze or mandatory restart.
The performance impact extends far beyond system sluggishness. Each antivirus program requires its own engine, its own signature database, its own real-time monitoring system, and its own firewall components. Running two simultaneously means doubling the CPU utilization, doubling the memory consumption, and doubling the disk I/O operations needed to protect the system. When a comprehensive scan is initiated on a system with two antivirus programs, the resource drain becomes particularly severe, as both programs scan the same files independently. Microsoft explicitly recommends against this practice, stating unequivocally that running multiple anti-malware apps at the same time can cause your system to be slow or unstable.
Compatible Tools That Work Effectively With Avast
While running multiple full antivirus programs creates irresolvable conflicts, Avast actually works well with specific supplementary security tools, particularly when those tools are designed as on-demand scanners rather than real-time protection systems. The distinction between on-demand scanning and real-time protection is crucial to understanding compatibility. On-demand scanners run only when the user explicitly initiates them, scanning the system for threats without maintaining constant background monitoring. Real-time protection systems, by contrast, continuously monitor file access and system activity, which is where conflicts arise with Avast’s own real-time protection mechanisms.
Malwarebytes represents the gold standard for Avast compatibility, particularly when using the free version. Users have reported no problems running Malwarebytes Free alongside Avast, and security professionals consistently recommend this combination for users who want a second opinion scanning tool to complement their primary Avast protection. The compatibility succeeds because Malwarebytes Free operates strictly as an on-demand scanner; it does not maintain resident real-time protection that would conflict with Avast’s core shields. Users can run manual scans with Malwarebytes regularly, perhaps weekly, to catch any threats that Avast might have missed, without creating the resource competition and file-access conflicts that plague other antivirus combinations.
SuperAntiSpyware (SAS) is another tool that integrates seamlessly with Avast, provided users employ the free version with on-demand scanning rather than activating the paid resident protection features. When properly configured, Avast Home, Malwarebytes Antimalware, and SuperAntiSpyware can work together without experiencing the conflicts and performance degradation that occur with multiple full antivirus packages. This trio represents the professional recommendation for users who want comprehensive multi-layered detection without the system instability that comes from running competing real-time antivirus engines.
HiJackThis is another utility that works well with Avast, though it requires clarification regarding its purpose and appropriate usage. HiJackThis is not a traditional antivirus program but rather a diagnostic tool that generates reports about system configuration, browser settings, and installed programs that might be malicious or suspicious. Users typically don’t need HiJackThis unless they suspect a particularly difficult-to-remove infection or are attempting to clean a computer that had inadequate protection previously. Because HiJackThis operates as a reporting and analysis tool rather than a continuous protection system, it creates no conflicts with Avast.
For supplementary anti-spam protection, Avast is compatible with several spam-filtering solutions including MailWasher (both free and professional versions), SpamPal, and Spamihilator. These tools address email-specific threats rather than system-wide malware, so they operate in a different functional space than Avast’s core antivirus engine. Spamihilator can be configured to work with Avast through specific configuration settings, allowing users to add spam protection without triggering the conflicts that occur with overlapping antivirus engines.
On-Demand Scanners as the Solution to Multi-Layered Protection
The solution to the common desire for multiple scanning opinions without creating system conflicts lies in understanding and utilizing on-demand scanners strategically. On-demand scanning tools operate under a fundamentally different model than real-time antivirus protection. Instead of constantly monitoring file access and maintaining resident protection in system memory, these tools are launched by the user when they want a scan performed, they execute their scanning procedures, identify any threats, and then terminate without maintaining ongoing presence on the system.
Users can think of on-demand scanning as analogous to taking a second opinion from a different doctor. When you have a health concern, you might consult one doctor, but if you want additional confirmation, you see a second doctor. The two doctors don’t interfere with each other; they simply provide independent analyses. Similarly, after running Avast’s built-in scanning, a user can run Malwarebytes Free for a second opinion, then run SuperAntiSpyware for a third independent perspective, and finally execute a portable scanning tool like Emsisoft Emergency Kit or Dr.Web CureIt without creating any of the conflicts that would occur if all these programs maintained constant real-time protection.
However, the critical caveat is that this approach only works when users employ the free versions of these tools or configure paid versions to operate in on-demand mode. If users purchase and enable resident protection for Malwarebytes, SuperAntiSpyware, or any other on-demand tool, that tool converts to a real-time monitoring system that will conflict with Avast’s own real-time protection. The difference is unambiguous: free versions of these tools simply do not offer real-time protection, so users cannot accidentally enable conflicting features. Professional versions do offer real-time monitoring, which would create the exact same conflicts that occur with multiple full antivirus programs if simultaneously enabled.
Dr.Web CureIt and Kaspersky Virus Removal Tool represent particularly useful portable scanning solutions for supplementing Avast protection. These utilities can be downloaded once and stored on the system, or even on a USB flash drive, then used whenever the user wants an independent scan. Dr.Web CureIt includes current virus definitions at the time of download but is not designed to provide continuous protection; instead, users should download the tool regularly whenever they want to perform a scan with the most current definitions available. This portable approach provides independent scanning capabilities without any of the background interference that creates conflicts with Avast’s resident protection.
Emsisoft Emergency Kit represents another award-winning portable solution that works without conflicts alongside Avast. This kit includes a dual-scanner technology that provides more comprehensive malware detection than either scanner alone, yet because it operates as a portable tool requiring explicit user activation, it creates no conflicts with Avast’s real-time protection mechanisms. Professional malware removal specialists specifically include Emsisoft Emergency Kit on their portable toolkit USB drives for exactly this reason—it provides thorough secondary scanning capability compatible with any primary antivirus.
Avast’s Performance in Independent Testing: Context for Compatibility Decisions
Understanding whether Avast itself is performing adequately helps inform decisions about whether additional scanning layers are even necessary. Recent independent testing from August 2025 by AV-Test, one of the most respected independent security testing organizations, showed Avast Free Antivirus 25.6 and 25.7 achieving a certified status with 91.7 percent protection scoring and 100 percent performance scoring and usability scoring. In comparative testing against 743 malware samples conducted by AV-Comparatives between July and October 2021, Avast One detected 742 threats to achieve a 99.9 percent protection rate with only two false positives. This performance essentially matches or exceeds most competing antivirus programs, suggesting that for most users, Avast alone provides adequate protection without requiring multiple additional scanners.
Furthermore, Avast received a maximum score of 6 in AV-Test’s Product Review and Certification Report, meaning Avast users receive 100 percent protection against zero-day threats and 99.80 percent against known malware. These metrics are particularly significant because zero-day threats represent vulnerabilities that no antivirus has yet identified or created definitions for—catching these represents the cutting edge of malware protection. The fact that Avast achieved perfect scores against these emerging, previously-unknown threats demonstrates that the core engine is sophisticated and effective. In April 2025 performance testing by AV-Comparatives examining the impact of various antivirus programs on system speed, Avast and AVG tied for second place with an AVC Score of 90 and a Procyon Score of 96.2, significantly outperforming Windows Defender’s 80 AVC score.
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Get Protected NowFor users who are concerned about particularly sophisticated threats, business-critical security, or ransomware attacks, supplementing Avast with on-demand scanning tools provides a valuable additional layer without the system instability that comes from multiple real-time protection engines. However, for typical home users with ordinary browsing and computing habits, Avast alone provides protection at a level that exceeds industry averages and independent testing standards. The decision to add supplementary on-demand scanners should be based on actual security concerns or professional requirements rather than a general assumption that more protection always means better protection.
Passive Mode: An Alternative for Users Requiring Multiple Antivirus Engines
For users who absolutely require running another full antivirus program alongside Avast—such as corporate environments with mandatory antivirus policies or users with highly specialized security requirements—Avast provides a Passive Mode option that represents a technical workaround, albeit with significant limitations. Passive Mode disables all of Avast’s active protection functions, including the Core Shields and Firewall, allowing another antivirus program to assume all real-time protection responsibilities. In Passive Mode, Avast still receives updated virus definitions and can perform manual scans upon user request, but it cannot actively protect the system.
The mechanism is straightforward: by disabling Avast’s active protection components, the system eliminates the core source of conflict—multiple programs attempting to monitor file access and intercept potential threats simultaneously. With Avast running only in passive mode, all real-time protection duties fall to the other antivirus program, preventing the resource conflicts and file-access battles that occur when multiple programs maintain active protection simultaneously.
However, Avast explicitly recommends enabling Passive Mode only temporarily for troubleshooting purposes, not as a permanent configuration. The reason is obvious: if Avast is not providing active protection, then the user is no longer benefiting from Avast’s presence; the other antivirus program is providing all protection. If the other antivirus program is the one actually providing protection, then the user would be better served simply uninstalling Avast and relying on that other program exclusively. Passive Mode exists primarily for scenarios where both antivirus programs are already installed and the user wants to troubleshoot configuration issues or temporarily test another antivirus while retaining Avast for manual scanning.
In practical terms, Passive Mode is not a recommended approach for long-term use. Users encountering situations where they feel they need multiple full antivirus programs should instead make a decisive choice, select the antivirus that best meets their needs, and uninstall the other programs. If they want additional scanning capability beyond their primary antivirus, they should adopt the on-demand scanning approach with tools like Malwarebytes Free or Emsisoft Emergency Kit rather than attempting to run multiple full antivirus engines, whether in passive mode or active simultaneously.
Professional Recommendations and Best Practices for Avast Users
Information technology professionals and security specialists consistently recommend against running multiple full antivirus programs and instead advocate for a layered security approach that combines one robust antivirus with specialized supplementary tools. Rather than seeking redundancy through multiple antivirus engines, professionals build security depth through functional specialization. Avast serves as the primary antivirus and real-time protection layer, Malwarebytes Free provides on-demand anti-malware scanning with a different detection methodology, and then additional specialized tools like password managers, firewalls, and VPN services add security layers focused on different threat vectors.
This approach recognizes that different security tools excel at different tasks. Avast’s core engine is excellent at detecting known malware through signature-based detection and identifying emerging threats through behavioral analysis. Malwarebytes approaches malware detection differently, using techniques that sometimes catch threats Avast misses, particularly certain browser-based exploits and potentially unwanted programs. Neither application provides optimal detection if somehow run simultaneously in real-time mode, but both applications provide optimal detection when used strategically—Avast as the always-on protection and Malwarebytes as a regular manual scanning supplement.
For users concerned about ransomware specifically, both Avast and Malwarebytes detect ransomware threats, but Avast’s premium versions add additional ransomware-specific protection through Ransomware Shield, which monitors for suspicious encryption activities and prevents unauthorized file access patterns. Users can evaluate whether this additional premium feature provides value for their threat profile, but if they determine that Avast Free is sufficient, adding Malwarebytes Free provides an additional scanning opinion without creating system conflicts.
Professionals also emphasize the importance of understanding the difference between potentially unwanted programs (PUPs) and actual malware. Many supplementary scanning tools detect PUPs—programs that are technically legitimate but may collect user data, display aggressive advertising, or modify browser settings without explicit consent. Avast includes options for detecting and blocking PUPs, so the distinction between the primary antivirus and supplementary scanners is not always absolute. Some users prefer conservative approaches that allow PUPs, while others prefer aggressive approaches that remove them. On-demand supplementary scanners allow users to adjust their detection sensitivity without affecting their primary antivirus configuration.
Alternative Antivirus Solutions and Competitive Landscape
While Avast represents an excellent choice for many users—with 435 million devices protected globally and consistent top-tier performance in independent testing—it is not the only option, and some users may prefer alternatives for various reasons. Understanding the competitive landscape helps inform decisions about whether to add supplementary tools to Avast or whether a different primary antivirus might better serve specific security needs.
Norton Antivirus represents the most significant competitive alternative to Avast, particularly given that Norton and Avast merged in September 2022 to form Gen Digital, creating a cybersecurity conglomerate that also owns AVG and CCleaner. The merger resulted in similar pricing and feature sets between Norton and Avast products, with Norton offering slightly more affordable entry-level pricing and potentially higher malware detection rates according to some independent tests. However, since both brands now operate under common ownership, the strategic choice between them is largely personal preference rather than fundamentally different company philosophies or security approaches.
Bitdefender Antivirus represents another competitive alternative known for exceptional malware detection rates and sometimes slightly lower system performance impact than Avast, though at a higher price point. Some users prefer Bitdefender’s interface or feature set, but the protection offered is comparable to Avast’s. Similarly, ESET Security products, Kaspersky Antivirus, and Trend Micro represent alternative full-featured antivirus solutions with comparable performance characteristics.
Rather than switching to a different antivirus entirely, most users are better served by continuing with Avast and adding supplementary on-demand scanning tools if they have specific security concerns. However, users experiencing compatibility issues or performance degradation with Avast might evaluate these alternatives, particularly if they represent significantly different company philosophies or feature sets that better match individual requirements.
Avast’s Recent Evolution and Corporate Integration
Avast’s evolution following the September 2022 merger with Norton into Gen Digital has important implications for users considering what security solutions work well with Avast. The merged company operates both the Avast and Norton brands as distinct product lines rather than consolidating them into a single offering. This means that while Norton and Avast now share underlying security technologies and threat intelligence networks, they remain separate products with distinct interfaces and feature presentations.
For Avast users, the merger has primarily been positive, significantly expanding the threat detection network to include both companies’ intelligence and adding new features like AI-powered scam detection through the Avast Assistant. The combined company’s scale and resources mean faster threat response, more comprehensive threat intelligence, and more funding for development of new protective features. The integration of Norton’s identity theft protection features into higher-tier Avast plans represents another benefit of the merger.
Users should be aware that Norton, despite now being under common ownership with Avast, remains a distinct alternative rather than a successor to Avast. Some users might prefer Norton’s pricing, interface, or feature set, but the choice between Avast and Norton is more about personal preference than about one being technically superior to the other. Both operate under the same parent company, both draw from the same threat intelligence networks, and both integrate with the same back-end infrastructure.
Supplementary Security Features Beyond Antivirus
Beyond antivirus and on-demand scanning tools, Avast users can enhance their security posture by understanding what supplementary features work well with Avast and which features Avast itself provides. Anti-spam protection is one area where supplementary tools can meaningfully enhance security, as email represents one of the primary attack vectors for malware distribution. Avast is compatible with MailWasher, SpamPal, and Spamihilator without creating conflicts, allowing users to add sophisticated email filtering to complement Avast’s web and file-based protection.
Web security represents another area where supplementary tools enhance protection. Browser extensions like Malwarebytes Browser Guard provide additional protection against malicious websites, phishing attacks, and browser-based exploits without conflicting with Avast’s own web protection features. These browser-based protection tools operate at a different level than system-level antivirus and can provide value without creating the conflicts associated with multiple system-level antivirus engines.
VPN services represent privacy enhancements that complement but do not conflict with antivirus protection. Avast offers SecureLine VPN as an add-on product that can be used alongside Avast’s antivirus protection without any technical conflicts. VPNs address different security concerns than antivirus—protecting network privacy and encrypting internet traffic rather than detecting and removing malware. Accordingly, VPNs from Avast or third-party providers can be safely combined with Avast’s antivirus protection.
Password managers similarly complement antivirus without conflict. Avast includes a password manager option in higher-tier subscription levels, and third-party password managers like Bitwarden operate independently of antivirus engines, providing no conflict whatsoever. Firewalls, both Avast’s own firewall (included in Avast Premium) and third-party firewall solutions, can also work alongside Avast without causing the system conflicts that occur with multiple antivirus programs, since firewalls operate at a different network layer than antivirus engines.
System Requirements and Compatibility Considerations
Users considering adding supplementary tools to Avast should verify system requirements and compatibility for both Avast and any supplementary software. Avast’s system requirements are modest—even older systems with 1 GB of RAM and 2 GB of hard disk space can run Avast Free Antivirus. Malwarebytes Free and other supplementary tools have similarly modest requirements, meaning compatibility is rarely a limiting factor.
However, cumulative resource consumption becomes relevant when running multiple tools. Even though individual tools have low system requirements, running Avast, Malwarebytes, and a firewall simultaneously will consume more system resources than running Avast alone. Users with older computers with limited RAM should be mindful of this cumulative impact and might choose to run supplementary tools during lower-activity periods rather than leaving them all active simultaneously.
Windows versions represent another compatibility consideration. Avast continues to support Windows 10 through October 2028, even after Microsoft’s official support for Windows 10 ends in October 2025. This extended support is important for users unable to immediately upgrade to Windows 11, as it ensures Avast protection will continue to work and receive updates even on out-of-support Windows versions. Most supplementary tools maintain comparable Windows support, so this generally is not a limiting factor for tool combinations.
Security Software Conflicts and Troubleshooting
Users who experience issues after installing supplementary security tools should understand the difference between expected minor performance degradation and actual conflicts indicating incompatible software. Installing any additional software will consume some system resources and may cause slight slowdowns in system responsiveness. However, significant performance degradation, frequent crashes, bluescreens, or system instability indicates actual software conflicts that require troubleshooting.
If users experience these symptoms after installing supplementary security tools, the first step is to verify that no full antivirus programs are running simultaneously. Many users inadvertently leave old antivirus software partially installed even after transitioning to new primary antivirus solutions. Remnants of previously installed antivirus programs can create conflicts with both the new primary antivirus and each other. Complete removal requires either using specialized uninstaller tools provided by antivirus vendors or, if those fail, using removal utilities provided by security companies.
Users experiencing conflicts should systematically disable each supplementary tool to identify which specific tool is causing problems. Often the culprit is a tool configured to run in real-time mode rather than on-demand mode, or a paid version of supplementary software that was supposed to operate in on-demand mode but was inadvertently configured for real-time monitoring.
Recommendations for Different User Profiles
Different users have different security needs and technical sophistication levels, which should inform decisions about what tools to combine with Avast. Typical home users with average browsing habits and no special security concerns are well-served by Avast alone, without supplementary tools. These users should not add additional antivirus engines or even on-demand scanning tools, as the minimal additional security benefit does not justify the added complexity and system resource consumption.
Users with higher risk profiles—such as small business owners, users handling sensitive financial information, or professionals managing important intellectual property—benefit from supplementary on-demand scanning with Malwarebytes Free on a weekly schedule. This approach provides an additional line of defense and a second opinion scanning mechanism without the system conflicts and resource consumption that would result from multiple real-time protection engines.
Users with specific threat concerns, such as those particularly worried about ransomware, should evaluate whether Avast’s premium features address those concerns before adding supplementary tools. Avast Premium Security includes Ransomware Shield, firewall protection, and advanced web protection that reduce the need for supplementary tools. For most users, the premium features of Avast address the majority of threat concerns better than attempting to add multiple supplementary tools.
Information technology professionals and security specialists managing multiple computers should understand that while individual users might benefit from specific supplementary tools, organizational deployments should standardize on a single primary antivirus solution and potentially add centrally managed on-demand scanning tools rather than asking every user to personally manage a complex security stack. This approach simplifies administration, ensures consistent protection levels, and reduces the likelihood of user misconfiguration.
Achieving Avast Harmony
The comprehensive analysis of antivirus tools that work well with Avast reveals a clear pattern: multiple full antivirus programs cannot coexist on a single Windows system without creating serious conflicts, performance degradation, and potential security loopholes, yet well-designed supplementary tools operating in on-demand mode create no conflicts and provide valuable additional security layers. This distinction between full antivirus programs and supplementary tools represents the critical insight that resolves the common confusion about running multiple security products simultaneously.
Avast is an excellent antivirus solution, earning consistent high marks in independent testing for both detection rates and system performance impact. For the vast majority of users, Avast alone provides adequate protection without requiring supplementary tools. The software protects 435 million devices globally, and its 100 percent protection rate against zero-day threats demonstrates the sophistication and effectiveness of its core detection engine.
Users who desire additional scanning layers should combine Avast with on-demand supplementary tools rather than other full antivirus programs. The gold standard approach pairs Avast with Malwarebytes Free or SuperAntiSpyware Free (in on-demand mode only), supplemented by portable scanning tools like Emsisoft Emergency Kit or Dr.Web CureIt. This approach provides multiple independent scanning opinions without creating the resource conflicts, system instability, and performance degradation that result from running multiple real-time antivirus engines simultaneously.
The fundamental principle is that security depth comes from functional specialization, not redundant duplication. Rather than seeking protection through multiple antivirus engines competing for system resources, users achieve better security through a combination of effective antivirus protection, supplementary on-demand scanning, firewall protection, secure browsing practices, regular software updates, and careful user behavior. Avast serves as an excellent primary antivirus component in this comprehensive security approach, and understanding which tools work well alongside it enables users to build a robust security posture without the system degradation that results from well-intentioned but technically problematic attempts to run multiple antivirus programs simultaneously.
