The answer to those questions was easy a decade ago. Today, the built-in security features in Windows, including the Microsoft Defender Antivirus engine, for example, pass the “good enough” test, making the choice less clear-cut.
But for some picky PC users, replacing the basic built-in antivirus protection with software from an outside developer is just natural when setting up a new PC. Even if the difference is small, it’s still an improvement. In a world where ransomware is an existential threat to businesses and banking-related Trojans and phishing attacks can drain your checking account in minutes, you want every edge.
The best-known commercial antivirus programs for Windows and Mac machines typically require an annual paid subscription, but some perfectly respectable names also distribute free versions of their software, usually for noncommercial use only.  Typically, these programs include the exact same scanning engines and malware definition files, minus most of the fancier features and, crucially, offering minimal support options. You can also expect frequent, occasionally annoying upsell offers as the developers try to convince you to upgrade to a paid plan. All of the programs we list here are completely free and are appropriate for use in a home setting by nontechnical users. Below, I’ve listed my top recommendations for free PC antivirus software. Also: The best antivirus software and apps (and why you need to protect your devices) After nearly a quarter-century with its free product in the US market, AVG has developed a solid identity as the go-to name in free AV software.  The AVG AntiVirus Free solution provides a real-time malware and antivirus scan, quarantine options, a file shield exceptions whitelist, deep and targeted scans, as well as the option to check external drives for suspicious programs. You can also opt to join the beta program in which you will have access to features in testing.  AVG AntiVirus Free tends to do well in independent testing, but they’re not shy about monetizing their customers. When you install the free product, some features will be masked in gray until you sign up for a paid plan. I personally find the “hacker attacks” protection button (a network inspector and ransomware shield on MacOS) irritating, as this could be considered a deliberate means to elicit fear in consumers. The basic virus-scanning tools in either product work as advertised. If you can ignore the frequent upgrade offers, it’s a perfectly good choice. Avira Free Security includes antivirus scanning, as expected, but it also includes extra modules intended to improve performance and safeguard privacy.  The performance tab of the Avira console includes options for cleaning up your system, uninstalling outdated apps, and deleting unnecessary files. Options on the Privacy tab include setting up a VPN and password manager. While the software’s tracking cookie cleaner is locked to paid subscriptions, the antivirus solution’s junk cleaner is quick and effective.  If you’re looking for free antivirus software with notable, extra features, Avira’s creation is the best option. Bitdefender, a privately held company based in Romania, has a solid reputation for its paid security products. Its free offering includes a minimalist interface, with no frills or extras, that’s free of upsell offers. Bitdefender Antivirus Free promises to keep your “computer running clean, fast & virus-free while shielding you from the latest e-threats,” and that’s what you get. It takes over the malware scanning and removal functions normally assumed by Microsoft’s antivirus software but doesn’t include additional features such as ransomware protection, system optimization, or a virtual private network, which are part of the company’s paid plans.  There are free versions available for MacOS and Android, although the reviews for the MacOS are mid-pack, at best. Malwarebytes offers a free tier for its reputable antivirus products. The software is compatible with Windows and Mac PCs, and there are also apps available for Android and iOS smartphones and tablets.  During scans, Malwarebytes can automatically quarantine suspicious software or apps. The interface is clean and simple to use, and you can also see reports on when a scan last took place – and whether or not suspicious files and software were found and removed. Furthermore, you can decide on the antivirus program’s CPU usage – high, medium, or low – and whether or not to quarantine or skip potentially unwanted programs (PUPs). When you install the software, there’s a premium trial that only lasts for a certain number of days. After your time expires and if you choose not to purchase a license, you will lose real-time protection and the option to run scheduled scans.  The best way to choose is to install a package and try it out for long enough to decide whether the interface and features of the free antivirus service suit you.  Most importantly, the software and accompanying services have to be completely free for long-term use, with no expiration date or hidden costs.  If you choose to install third-party security software, Windows automatically disables the corresponding Microsoft Defender features. Security software makers pay for the privilege of participating in these tests, which use a mix of known malware samples, suspicious website behaviors, and other indicators to measure success. The difference between a 98.4% rating and a 100% rating is insignificant, especially considering how many other layers of security can prevent an executable file or script from landing on your desktop in the first place. In addition, a 100% rating means only that the software successfully passed all the challenges it faced in that month’s test cycle. It doesn’t mean you’ll be 100% protected from a malicious download or email attachment. The catch, of course, is that the discount is only good for the first year. When renewal time comes around, those discounts are much harder to find. The overall prices vary dramatically, depending on which features are included and how many devices the subscription supports.