Can you use two antivirus programs on one computer?

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4. More isnt always more: Little advantage for high resource cost

This is actually the strongest reason against running two full protection systems simultaneously. Virus/malware protection products today are rather complex and the exponentially growing number of threats (it doubles every year) requires a lot of code to keep the computer safe. This naturally results in a relatively high usage of computer resources, especially its memory (RAM). By running two full antivirus programs all the time, you’re basically wasting resources, because 90 percent or more of their functionality will be the same. All available protection products of reputable vendors today operate on very high quality standards and detection rates often only differ by about 1-2 percent according to test labs.

So, you might end up spending 0.5 to 1 GB or more of your available RAM to bring your detection rate up from, say, 98 percent to 99 percent. But is this minuscule improvement really worth it? Every new file on the computer would need to be scanned by both products, triggering two complex sets of code that use a lot of your CPU time, which could undoubtedly be better used for other tasks – you know, stuff you actually want to do on the computer.

The better option is to go for one product that comes with multiple scanning engines that are tuned to work together seamlessly, or a product that uses a layered protection approach with different technologies, or, better still, a product that implements both.

Is It Bad to Have Multiple Antivirus Programs and Why?

While it may seem like a good idea to have multiple antivirus programs running on your PC, it’s not. Logically, you would think that it would give you additional security. In most instances, it’s quite the contrary. Your good intentions may have dire results. Here are a few reasons why you should not run multiple antivirus programs on your PC: 

A heavy and unnecessary toll on system resources

Running a single heavy-duty anti-virus can be quite taxing on your system. Trying to run multiple antiviruses can slow your system down to a crawl especially if you do not have a high-end system.

We would especially advise against running multiple antiviruses on a laptop, especially if you’re powering it using its battery. Anti-viruses can draw a lot of processing power and memory which will, in turn, draw more energy.  

Even if your computer can handle the system demand, you are still likely to run into freezes and crashes.


Multiple antiviruses may interfere with each other. Often, antiviruses are as intrusive as the viruses they aim to combat. If you are running multiple antiviruses, the chance of them encountering false positives increases.

When your anti-virus detects suspicious programs, it moves them to a quarantine vault, unless you specify otherwise. If both antiviruses run simultaneous scans, they may both detect the same suspicious program or file. This may cause a conflict that causes one of your antiviruses to temporarily stop – or even worse – cause your operating system (especially if it’s Windows) to crash.   

Additional Admin

Configuring and running a single anti-virus can take considerable admin. Modern antiviruses come with a host of configurable features. You need to decide which ones your system requires. 

With the growing complexity of anti-viruses, configuring each takes considerable time and effort. Furthermore, when each antivirus finds a threat, you need to specify how it deals with it. You’ll also need to set scan exceptions (if you have any) for each antivirus.   

Accusing One Another

The worst effect of multiple antiviruses working in tandem is that they won’t trust one another. When an antivirus does its job, it assumes it’s the only one installed. Therefore, if they detect a second antivirus scanning through files, they’ll assume it’s actually a virus. At best, you’ll be bombarded with false virus alerts when the antiviruses spot one another. At worst, they may begin trying to delete each other’s files which will lead to system instability and important files being corrupted.

Alternatives to Running Multiple Antivirus programs

You don’t have to run permanent multiple antiviruses to get a second opinion scan. Companies like ESET have free online scanners on one-time scans that you can download.

If your antivirus doesn’t come packaged with a certain feature, you can download or purchase an alternative application. For instance, if you want a more comprehensive firewall feature, why not download TinyWall

Types of programs that can cause conflicts

The following types of programs should not run concurrently:

  • Antivirus and antispyware real-time scanning programs such as Norton AntiVirus, Symantec Endpoint Protection, McAfee VirusScan, or Kapersky AntiVirus.
  • On-demand scanning programs, such as the Windows Malware Removal Tool.
  • Single-use malware removal tools that are designed to remove files from individual threats.

Occasionally run second opinion scans

We encourage you to check your protected system with a second opinion scanner from time to time, just to be sure that your main antivirus/antimalware hasn’t missed anything. Scanner-only products typically don’t have any issues running alongside protection products so it’s safe to use them.

Cloud based scanners are nice light-weight options here. Alternatively, if you’re not using Emsisoft Anti-Malware to protect your computer, you can use our free Emsisoft Emergency Kit, which is the only fully featured dual-engine scanner available and doesn’t even require installation to check your PC for threats and unwanted programs (PUPs).

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Have a malware-free day!


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