Why most antivirus apps slow your laptop to a crawl
25 Jun 2026 · 2 min read · Comments
This article contains affiliate links. If you buy through them, we may earn a commission — at no extra cost to you.
The laptop was fine before the renewal. Then the antivirus ran a full scan, the fan kicked in, everything slowed to near-freeze, and you started wondering if the cure was worse than the disease. It isn't — but the product might be wrong.
Antivirus software has to examine files. That examination takes CPU cycles, memory, and disk I/O. The question is how much — and whether the product is designed to minimise its footprint or simply get the scan done regardless of what else is running.
Independent testing by Tom's Guide found that some antivirus products slow a laptop by as much as 96% during a full scan: the measured example being McAfee on a standard consumer laptop. That's near-total performance collapse during the scan window. Enough to make it impossible to work, stream, or do anything else.
Why the slowdown happens
The AV-TEST performance score
AV-TEST — the independent lab that rates antivirus products quarterly — specifically measures performance impact as one of its three scoring categories. The test measures slowdown when launching popular websites, downloading files, installing software, and running common applications while the scanner is active.
TotalAV consistently earns a passing score in this category. Products that fail it — or score near the minimum — are the ones that make your machine unusable during scans. The difference between the highest-rated and lowest-rated products in this test is often dramatic on older or mid-range hardware.
- TotalAV uses a cloud-assisted scanning approach that reduces local CPU load
- Smart scan scheduling: defaults to running when the machine is idle
- Startup optimiser removes the bloatware that makes many laptops slow before any scan runs
- Real-time protection runs in the background at negligible CPU cost
If your laptop runs noticeably slower since you installed your antivirus, that's the product's design — not a necessary cost of protection. Switching to a lighter-footprint suite solves it without sacrificing detection rate.
Frequently asked questions
Do I need antivirus if I have Windows Defender?+
Windows Defender covers known threats but misses a significant share of new and polymorphic malware. AV-TEST data shows third-party tools like TotalAV achieve 99%+ detection rates versus Defender's lower real-world scores on novel threats.
How much does a good antivirus cost?+
TotalAV starts at $19/year for up to 6 devices — a fraction of what Norton charges at renewal ($94.99/year for Standard). Most users don't need the most expensive tier; entry-level paid antivirus outperforms free options in independent lab tests.
Can a Mac get a virus?+
Yes. Mac malware has grown significantly — AV-TEST catalogues hundreds of thousands of macOS-specific threats. Macs are safer than Windows by default but not immune, particularly to adware, browser hijackers, and phishing-delivered malware.
