You don’t need to pay for antivirus software in 2026. Seriously. The free protection built into Windows and macOS, combined with a few sensible habits, stops the overwhelming majority of threats — and in independent lab tests, the free options score as well as or better than many paid products. Here’s how to protect your computer from viruses for free, without spending a penny or installing sketchy “PC optimisers”.
Protect computer from viruses free: the protection you already have
Windows: Microsoft Defender. Every Windows 10 and 11 PC comes with Defender built in, and it’s genuinely good now — a far cry from the joke it was a decade ago. Independent labs (AV-Test, AV-Comparatives) consistently rate it among the top performers for detection, and it’s lightweight, silent and automatically updated. If you have Windows, you already have excellent antivirus. The biggest mistake people make is installing a second antivirus on top, which causes conflicts and slowdowns. One antivirus: Defender. Done.
Mac: XProtect and Gatekeeper. macOS has built-in malware scanning (XProtect, updated silently by Apple), Gatekeeper (blocks unverified software), and Safari’s fraud warnings. Macs get fewer viruses than Windows PCs — partly smaller market share, partly Unix architecture — but “fewer” isn’t “none”. Mac malware exists and is growing, mostly arriving as fake software downloads and trojanised apps.
Both: Your browser is a layer of defence too. Chrome, Edge, Firefox and Safari all warn about dangerous downloads and phishing sites. Keep your browser updated — those updates include security fixes.
The habits that stop 99% of infections
Here’s the uncomfortable truth: antivirus catches the threats, but you invite most of them in. The vast majority of infections start with a human clicking something. These habits matter more than any software:
- Don’t open unexpected attachments. “Invoice attached” from an unknown sender, a “parcel redelivery” ZIP file, a Word doc that asks you to “enable macros” — these are the classic infection routes. When in doubt, don’t click. Verify through another channel.
- Download software only from official sources. The vendor’s own site, the Microsoft Store, the Mac App Store. “Free” versions of paid software from random download sites are malware delivery vehicles — cracked Photoshop, free Office activators and game cheats are among the most infected files on the internet.
- Keep everything updated. Windows Update, macOS updates, browser updates — install them promptly. Most updates patch security holes that malware actively exploits. Turn on automatic updates and stop postponing them.
- Use an ad-blocker. Malicious adverts (“malvertising”) on legitimate sites are a real infection vector. uBlock Origin (free, for all major browsers) blocks them and makes the web faster as a bonus.
- Be sceptical of pop-ups. “Your computer is infected! Call this number!” — that’s the scam, not a warning. Real antivirus never asks you to call a phone number. Close the tab.
- Use strong, unique passwords plus two-factor authentication. Much “hacking” is just credential reuse — one breached site’s password tried everywhere. Our guide on setting up two-factor authentication is essential reading.
Should you install a free third-party antivirus?
With Defender this good, most people don’t need to. But there are legitimate reasons some do: a second-opinion scanner for a suspected infection, or slightly better phishing protection. If you want one, stick to reputable names with genuinely free tiers — Avast Free and AVG Free (same company) score well in labs, and Bitdefender Free is lightweight. Avoid anything you’ve never heard of, anything advertised via pop-up, and anything promising to “speed up your PC” alongside virus protection — that’s the language of scareware.
One firm rule: never run two real-time antiviruses simultaneously. They fight each other, slow your PC to a crawl, and can actually reduce protection. If you install a third-party antivirus, it should automatically disable Defender’s real-time protection — that’s normal and correct.
The free second-opinion scanners (for when something feels wrong)
If your computer is acting strangely — sudden slowdowns, pop-ups, browser redirects — but your main antivirus says all clear, get a second opinion from an on-demand scanner (these don’t run constantly, so no conflicts):
- Malwarebytes Free — the gold standard second opinion. Its free tier scans and removes on demand. Run it, remove what it finds, done.
- Microsoft Safety Scanner — Microsoft’s own on-demand tool, free, no installation.
- ESET Online Scanner — free browser-based scan from a respected vendor.
If these find something serious (a rootkit, ransomware), consider a full Windows reinstall after backing up documents — it’s the only way to be sure a deep infection is gone.
Backups: your ultimate free protection
No antivirus is perfect, and ransomware — which encrypts your files and demands payment — is the threat that makes backups essential. Windows File History and macOS Time Machine are free and built in. A £50 external hard drive plus automatic backups means ransomware goes from catastrophe to inconvenience. Cloud storage helps too — see our comparison of free cloud storage options. The 3-2-1 rule: three copies, two different media, one off-site. Even two copies in two places covers most disasters.
What about phones and tablets?
Phones are less vulnerable — iOS and Android sandbox apps aggressively, and most “phone viruses” are actually just scammy apps or phishing. The free protection: install apps only from the official stores, keep the OS updated, don’t sideload APKs from random sites, and review app permissions (our guide on stopping apps tracking your location covers the privacy side). You don’t need antivirus apps on your phone — and many “free antivirus” apps in the Play Store are junk or adware themselves.
The bottom line
Spotting phishing: the skill no software replaces
Most “virus” problems in 2026 aren’t viruses at all — they’re phishing: fake emails, texts and calls tricking you into handing over passwords or installing malware yourself. Learn the tells: urgency (“your account will be suspended in 24 hours”), unexpected attachments, sender addresses that look almost right (micorsoft-support.com), and links that don’t match the claimed destination (hover before clicking). Banks, HMRC and delivery companies never ask for passwords or bank details by email or text — [Action Fraud](https://www.actionfraud.police.uk) reports thousands of cases yearly from people who didn’t know that. If a message makes you anxious, that’s the point — slow down, verify through the official website or app directly, and never call a number provided in the suspicious message itself. Forward scam texts to 7726 (free) to help networks block them.
Verify any antivirus claim against AV-Test’s independent lab results — real detection data, updated constantly.
Protect your computer from viruses for free with: Microsoft Defender (Windows) or macOS’s built-in tools — already installed, already excellent; automatic updates switched on; downloads only from official sources; an ad-blocker; and healthy scepticism about attachments and pop-ups. Add Malwarebytes Free as a second-opinion scanner and a proper backup routine, and you’re better protected than most people paying £50 a year. The software is free — the discipline is the part that counts.
