Does Antivirus Slow Down Your Computer?

In today's threat landscape, antivirus software is crucial for keeping you protected from spyware, ransomware, identity theft, and phishing attempts. But performance concerns are a real barrier to adoption — our antivirus survey found that 16% of people who don't use antivirus software cite device slowdown as their reason for avoiding it.

The good news: a slow computer isn't always the antivirus's fault, and even when it is, there are usually ways to fix it without sacrificing your protection. But how do you know when the culprit is your antivirus, a malware infection, your internet connection, or your hard drive?

Disabling your antivirus temporarily and rebooting is an excellent start to diagnosing the problem. If your computer runs noticeably faster, the antivirus is likely contributing to the slowdown. There are ways to optimize your software if that's the case — and other options if you think it's time for a change.

Will antivirus software slow down my computer?

It depends. A variety of factors determine whether antivirus software will meaningfully impact your computer's performance:

• How old is your computer?
• Is the program known for high resource usage?
• How much processing does the antivirus do locally versus in the cloud?
• Is there bloatware on your machine that might be contributing to the slowdown?
• What operating system are you running?

All of these factors come into play when determining whether the problem is your antivirus or your machine.

If you're doing heavy video editing while streaming music and running a memory-intensive antivirus on a computer that isn't built for that workload, you'll almost certainly see a slowdown — but the antivirus may only be part of the equation. On the other hand, if you're browsing the web on a modern device with a cloud-based antivirus active, you'll likely not notice it at all.

Cloud-based antivirus programs are generally the most performance-friendly. By routing the heavy processing work through remote servers rather than your local machine, they protect you without significantly increasing your CPU usage. Good cloud-based programs also maintain a degree of offline protection, so you're not left vulnerable without an internet connection. 

For a look at how this works under the hood, see our guide on how antivirus software works.

How to know if your antivirus is slowing down your device

The clearest way to test this is to disable your antivirus completely, make sure it isn't set to restart automatically, then reboot your computer. If you notice your machine running faster, your antivirus is likely the culprit.

A few other signs that your antivirus may be affecting performance:

• Scans take over an hour to complete.
• Your computer becomes unusable during scans.
• The computer runs hotter than normal or more frequently.
• The computer crashes or freezes.

Most antivirus programs use some CPU during a scan, even cloud-based ones. A well-designed antivirus minimizes this by doing the bulk of its work off your device. If you're protecting an older computer, a cloud-based antivirus can be the difference between a usable machine and one that grinds to a halt during scans.

If performance issues are a top priority for you, our best lightweight antivirus guide covers the programs our testers found to have the smallest footprint without sacrificing meaningful protection.

How to choose a good antivirus

Performance matters, but a lightweight antivirus that doesn't protect you effectively is a bad trade. Here are the key features to look for when choosing a security suite that balances protection and speed.

Zero-day protection

Whether it's called zero-trust, zero-day, application whitelisting, or application allowlisting, the structure is the same: your antivirus checks everything your computer encounters and evaluates whether it's safe. You may experience occasional false positives with this feature, but it's a far better outcome than letting an infection through.

Cloud-based scanning

Cloud-based scanning routes the majority of processing work through remote servers rather than your local machine, allowing the antivirus to protect you without significantly increasing CPU usage or causing slowdowns. This is one of the most important features to look for if performance is a concern.

Tune-up tools

Some antivirus programs include built-in tune-up tools that clean out unnecessary files, optimize system configurations, and help your computer run at its best. These can be a useful bonus, especially on older machines.

Real-time protection

Real-time protection continuously monitors your system for potential threats as they happen, rather than catching them after the fact during a scheduled scan. This means fewer intensive full-disk scans, lower average CPU usage, and less overall slowdown — making it one of the most performance-friendly approaches to antivirus protection.

Scheduled scans

If you want to use your computer without battling your antivirus for resources, the ability to schedule scans is essential. Running a full scan overnight while you're sleeping lets the program do its most intensive work without affecting your day-to-day experience.

File caching

File caching allows your antivirus to remember files it has already verified as safe, so it can skip them on future scans. This reduces both scan time and CPU usage over time, as the program builds up a library of trusted files on your device.

Regular updates

Malware evolves quickly, and your antivirus needs to keep pace. Out-of-date software has been responsible for many preventable infections. Look for a program that releases regular definition and software updates, ideally automatically.

Third-party test scores

Independent labs like AV-TEST and AV-Comparatives evaluate antivirus programs across protection, performance, and usability. Checking a program's scores before committing is one of the most reliable ways to assess whether it will protect you without slowing you down. 

Our best antivirus software guide uses these scores alongside our own hands-on testing to identify the top performers.

Top antivirus solutions for performance

Tips to speed up your device

If your computer is running slow and you suspect your antivirus software, try the steps below before switching programs. In many cases, a few adjustments are all it takes.

• Run a full scan — you may have malware causing the slowdown, independent of your antivirus.
• Run your antivirus program's built-in tune-up tools if available.
• Close unnecessary programs running in the background.
• Disable any competing antivirus programs — running two at once is a common cause of slowdowns.
• Schedule full scans to run while you're sleeping (you'll need to leave your computer on).
• Update your antivirus to the latest version.
• Delete unnecessary programs and files to free up storage and memory.
• Disable unnecessary startup programs.

That last step is worth expanding on. Too many programs loading at startup can consume processing power before you've even opened a browser. 

How to manage startup programs by operating system

Windows 10 and 11

Windows key + X > Task Manager > Startup tab > right-click the programs you want to disable > select Disable.

Windows 8

Windows key + X > Task Manager > Startup tab > right-click the programs you want to remove > select Disable.

Windows 7 and older

Start > System Configuration > Startup tab > uncheck the programs you don't want loading during startup.

Bottom line

Antivirus software can slow down your computer — but it doesn't have to. Our antivirus survey found that while 16% of non-users avoid antivirus software due to performance concerns, three-quarters of people who do use it say it's effective at keeping them protected. The right antivirus, properly configured, gives you both.

Look for a cloud-based program with real-time protection, scheduled scanning, and strong third-party test scores. If you've followed the optimization steps above and your current antivirus is still causing problems, it may simply be the wrong tool for your machine. Our best antivirus software roundup covers top performers across all use cases.

Security software is necessary for staying protected online, but you shouldn't have to choose between protection and a usable computer. With the right program and a few maintenance habits, you can have both.

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