We test and rate free antivirus programs from companies you probably didn't even know offered security software for free. Here's the best free antivirus software you can get in 2017.

See also: Best antivirus 2017

There is no excuse for not having AV protection on your PC. None. Because there are lots of free antivirus packages, you can't use the cost as an excuse.

The good thing about having a free product from one of the leading Internet Security (IS) companies is that they use the same AV engine as in their paid-for products. What you get in the free version is stripped down package with a smaller feature set. Few include extras such as spam filtering, improved firewalls, parental controls, password managers and support for mobile devices. 

The free offerings from Avast, AVG, Avira, Bitdefender and Panda all fit this bill, yet all offer basic antivirus and anti-malware protection, giving you a good chance to keep your PC free of threats which could lose you data and take a lot of time to put right.

Since testing antivirus software with real malware requires a lot of time and effort, not to mention extremely specialist knowledge, we don't do this ourselves. Instead, we use the results from several well-respected independent test houses, including SE Labs, AV-test.org and AV Comparatives. 

AVG’s privacy policy, showing what rights it takes over your personal and non-personal information when you download and use its free product, has caused quite a furore since it was published around a year ago. You grant it the right to send some of your information to third parties, which may include advertisers.

Some have said ‘Well, this is just AVG being more upfront about its policy; they all do it’, so we checked at what each company says in its privacy policy. They’re not all the same: some require you to opt out to prevent sharing – and AVG says it will offer this – some ask you to opt in, but will respect your decision if you don’t, and some don’t share your information at all with third parties.

Best is Bitdefender, which claims not to share information with anybody outside its own company or subsidiaries. We think this is as it should be with a security product, but second-best is the assumption not to share, with an opt-in, should you want to receive ‘relevant’ offers. This is what Avast and Avira do. Panda does the same as AVG, requiring you to specifically unsubscribe to avoid security-related emails.

Internet security software is designed to prevent damaging programs from infecting your PC and laptop. All the free products here do that. As a secondary task, though, the full paid-for products should reduce the amount of unwanted advertising and offers that get through to you, and they usually offer quite a few other features as we mentioned above.

But without further ago, here are the leading free AV programs – you really can get something for nothing.

Best free antivirus software 2017

Best free antivirus: Avira

Download from Avira 

Avira has previously topped our list of the best free antivirus programs, and it’s still a very strong contender. We like that you can download the full program as well as just the 4MB launcher, giving you the option to start the installation and then leave it to download the rest. It’s not alone in this, but it’s the only one we know of which also lets you download the full thing.

The interface is well designed and easy to use, and the latest version includes a couple of new features in its SearchFree Toolbar: a website safety advisor and the option to block advertising companies from tracking you online.

At first sight, it appears Avira bundles a firewall with its product, but this turns out to be an integrated front-end to the Windows firewall.

File scans can be scheduled and by default there’s a quick scan set to repeat every 168 hours or, as we techies call it, weekly. We reckon a quick scan could run more frequently than this, though.

A year ago, AV-Test gave Avira perfect scores, and this year it still did commendably well. In its recent tests, it handed a 5.5 for protection and the same for performance. Avira achieved the full 6/6 for usability with no false positives or false blockages.

SE Labs didn’t test Avira in its recent roundup, but AV Comparatives gave Avira full marks for blocking 100 percent of threats.

Ultimately, Avira does an excellent job – even when compared to paid-for Internet Security programs.

Best free antivirus: Avast

Download from Avast

Unlike some firms, Avast doesn’t hide its free antivirus offering so you can’t find it. A big orange button on its homepage makes this version more obvious than its paid offerings, so it’s a good start.

As well as basic antivirus protection, it offers protection from unknown threats and a handy password manager so you can log into sites in your browser by remembering just one password.

You don’t get the browser extension that warns of fake sites (such as banks), nor a privacy shield or spam filtering. Those come with Avast’s Internet Security package, while Premier adds automatic software updating and a file shredder.

The good news is that Avast’s antivirus protection is excellent. SE Labs rates it at 94 percent overall, the highest score awarded to a free version. AV Comparatives found that it blocked 99.7 percent of threats in its September 2016 tests. It also found that Avast had the least impact on your PC’s performance – thanks in part to the fact that Avast runs a “significant proportion” of its analysis in the cloud.

AV-Test rates protection, performance and usability, giving Avast 5.5, 4.0 and 5.5 out of 6 respectively.

Overall, then Avast is one of the best free antivirus packages around.

Best free antivirus: Bitdefender

Download from Bitdefender 

Bitdefender’s paid-for Total Security package is excellent, and it’s no surprise to see its free offering score well: it uses the same virus detection engine.

In fact, AV Comparatives awarded it the unbeatable score of 100 percent, successfully blocking all malware during its tests in September. There were no false-positives, either, which is when safe files or programs are reported as being unsafe.

AV-Test also praised Bitdefender, giving it full marks for protection, performance and usability.

SE Labs’ tests found it wasn’t infallible though, with it being compromised by a number of threats and awarding it a protection rating of 73 percent.

Overall, Bitdefender is easy to use, is lightweight and – in general – offers good protection for your PCs. You can read our full Bitdefender Total Security 2016 review for more details.

Best free antivirus: AVG

Download from AVG

We’ve already mentioned AVG’s controversial privacy policy above, but in terms of the protection this free antivirus package offers, it’s not bad at all. SE Labs gave it an overall rating of 89 percent from its test in July-September, and it missed out on an AA award (rather than A) by only one percent.

AV-Test’s results from testing in July-August showed that its protection was above the industry average and awarded it 5.5 out of 6. It achieved the same for performance, so won’t slow your computer down. Again, it was given the same high score for usability, and as we’ve used AVG Free on our own PC for the past year, we can – anecdotally – agree that it runs transparently in the background and you don’t really notice it. And that’s exactly what you want from your antivirus.

AVG has a simple-to-understand dashboard so, if you do ever venture to it, it’s very clear whether it’s up to date and protecting your PC.

In addition to an AV engine, it also warns you of unsafe web links and can block unsafe email attachments.

Best free antivirus: Microsoft

Windows Defender is built into Windows 10 and Windows 8, so it’s arguably the easiest option for most people since it’s probably in operation already unless you’ve disabled it or installed another antivirus program.

Unlike in the past, when it merely paid lip-service to virus protection, the modern Security Essentials is a credible and reliable AV engine. OK, it’s not the very best out there, but it certainly does the job.

If your PC or laptop is running Windows 7, you can download Microsoft Security Essentials for free.

As the name suggests, it offers basic antivirus protection. The only difference between MSE and Windows Defender is that the latter offers better protection against rootkits and Bootkits.

SE Labs awarded MSE 91 percent overall, ahead of Bitdefender (90) and AVG Free (89). It was only three percent behind Avast, too.

AV-Test gave it only 3.5 out of 6 for protection, but this was due to a poor result in August of 88 percent. In July, it performed as well as any other antivirus package. AV Comparatives found it blocked 96.2 percent of threats, which is below all the other packages here, but as ever, these results all change on a monthly basis.

There are better choices than Security Essentials, but if you’re running Windows 8 or 10 with Defender built in, all you need to do is check that it’s enabled.