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Best Free Antivirus: 6 tried and tested ways to stay safe online

Trusted Reviews breaks down the best free antivirus packages you can get. Every item has been thoroughly reviewed for effectiveness and usability

Antivirus software is essential if you plan on going online, thanks to the proliferation of contaminated advertising iframes, malware-laden spam and drive-by downloads that can affect even the most legitimate, upstanding and popular of websites.

The following reviews were based on data gathered in the first six months of 2019. Our reviews pull together data from the respected AV-TEST and AV-Comparatives anti-malware and security testing labs to assess the performance of each antivirus program.

They test the software’s ability to correctly identify malicious files and websites, protect against drive-by downloads and avoid false positive detections, where benign software is incorrectly blocked as malicious.

Both labs also assess the impact of antivirus software on system performance. In addition to data from these established testing facilities, we test each antivirus suite ourselves to see what it’s like to live with and what features it provides.

While almost all of the antivirus tools we’ve reviewed did a decent job of protecting against malware, Kaspersky Free Antivirus 19 has the most consistently effective malware detection engines weve seen in a free product. It also has a minimal impact on system performance.

Avira Free Antivirus also put in a perfect detection performance in the latest tests, although AV-Comparatives found it to have a surprisingly heavy impact on system performance when downloading and installing software.

If you’d rather not install anything at all, Microsofts integrated Windows Defender is conspicuously hassle free – it works out of the box when you install Windows 10 and performs just as well as most third-party alternatives.

Related: Best Antivirus

A perfect choice for free antivirus

Kaspersky Free Antivirus review

Email scanning module | Bootable rescue disk available as separate download


  • Outstanding malware detection performance
  • Pop-up free silent detection mode
  • Low impact on system load


  • Lack of dedicated test results for free version

Why we liked Kaspersky Free Antivirus 19

Kaspersky Free Antivirus uses the same detection engine as the company’s well-regarded commercial products, which puts it among some of the best performing anti-malware tools around.

On installation, you’re asked to agree or opt out of recommended settings that will automatically delete malicious tools, adware, auto-dialers and suspicious packages and detect other software that can be used by criminals to harm your computer or data. You can change these settings at any time

You’re also prompted to create an account, but you can back out of this as it isn’t required to use the software. Kaspersky Free installs with a 366-day licence that auto-renews when it runs out.

The desktop client closely resembles its paid-for counterpart in its clean look and feel, with a main screen that displays your protection status and options to scan your system, update its virus database and open extra tools. A number of other options are greyed out, prompting you to buy one of Kaspersky’s paid-for anti-malware suites if you click on them.

Kaspersky Free comes with a browser plugin to check for malicious links in your search results. We were pleased to find that this doesn’t change your default homepage or search engine, although by necessity it requires permission to read all your browser data.

File, web, instant messaging, network and mail scanners are included, but you can’t customise or disable any of Kaspersky’s protection settings in this free version. Advanced options allow you to set how paranoid the scanner is, schedule scans and configure the program’s default behaviour and which notifications you get.

Unfortunately, this free version of Kaspersky’s software doesn’t make a regular appearance in most anti-malware testing labs’ results. Because of this, we’ve had to rely on performance figures for Kaspersky’s other products using the same engine.

While their performance should be the same in both real-world and reference tests, the slight uncertainty resulting from this extrapolated methodology remains our only caveat on what appears to be a perfect choice for free virus protection.

Kaspersky’s engine defended against 100% of reference samples and real-world malware exposures across two successive months of trials by AV-TEST and in AV-Comparatives’ test. In AV-Comparatives’ real-world malware exposure tests, it defended against 99% of malware with no false positives.

AV-TEST performance data shows that it had a heavier impact on website load times than most rivals, particularly on a low-power Core i3 system. AV-Comparatives’ tests don’t reproduce this, but instead indicate slightly slow first run times for both application launching and file copying.

However, both found that, overall, its system performance was less or at least no more obtrusive than most rivals.

  • Windows Vista/7/8/8.1/10
  • Requires Intel Atom 1.6GHz or faster
  • 1GB RAM
  • 920MB free disk space
  • 64MB Intel GMA950 video card or better
  • Screen resolution of at least 1024×600


Get Kaspersky Free Antivirus here

Windows’ own built-in protection is actually very good

Windows Defender AntiVirus 2018

Built into Windows 8/8.1/10Available for Windows Vista/7 as Microsoft Security Essentials | Will run on any Windows systemBootable Windows Defender Offline rescue disk available as separate download


  • Excellent Windows 10 interface
  • Good malware detection performance
  • No need to install third-party software


  • System impact isn’t as low as you might expect

Why we liked Microsoft Windows Defender

Microsoft’s Windows Defender – the default virus protection built into Windows 7 and above – has gone from strength to strength in recent years, and its performance in recent tests by multiple independent firms has been conspicuously good.

Its impact on system performance isn’t bad and is likely to be unnoticeable on most PCs. In fact, it slows down website launches noticeably less than most of its rivals. However, using it in favour of third-party software may not provide the kind of performance boost you’d hope for.

AV-Comparatives’ performance tests found that every single other free antivirus suite had less of an impact on overall system performance than Windows Defender, which particularly slowed file copying and installation operations. AV-TEST’s results confirm the slow install times, although the firm had fewer issues with file copies.

Windows Defender’s appearance and features vary depending on which version of the operating system you’re running it on. Windows 10’s Windows Defender Security Centre opens on a home screen with an overview of your protection status, including when Defender last updated and scanned for malware.

It also has dedicated tabs for different features. Virus and threat protection is home to your usual quick, full and custom scans, plus an intensive offline scan mode to tackle hard-to-remove threats. You can manually update virus definitions and enable or disable options such as cloud-based protection and real-time protection – the latter isn’t a good idea.

The device performance and health section monitors anything that might go wrong with your system over time and gives you a ‘Fresh start’ option that reinstalls Windows while keeping your files and most settings.

The firewall has its own tab where you can open ports, configure notifications and set different settings for private and public networks. App and browser control allows you to set the strictness of Microsoft’s SmartScreen utility, which can warn against or block apps that Microsoft’s remote verification service hasn’t seen before.

You can even disable notifications from Defender via the Virus & threat protection settings, giving it a very welcome silent detection mode.

Parental controls can be found under Family options. These provide device and account management for children who use Windows devices, allowing you to enable content filtering for the web, control the apps they install and the amount of time they spend in front of the screen.

Ransomware protection and file recovery are recently added features which relies on Microsoft OneDrive as a secure backup target, although you only get 5GB of free space by default.

Although Windows Defender hasn’t always had the best performance over the years, recent test results have been excellent.

In AV-TEST’s latest results, it protected against all reference samples and almost all real-world malware exposure tests over a two month period – slipping to 99.9% in February’s real-world malware exposure test. AV-Comparatives’ real-world tests confirmed the trend, giving Windows Defender an accuracy rate of 100%.

Microsoft’s integrated antimalware suite is currently so effective that, unless you need specific features or a slight performance boost, there’s little point in installing third-party antivirus software.

  • 1 GB RAM or higher
  • 500 MB hard disk space
  • Screen resolution of at least 800 x 600


Get Microsoft Windows Defender here

Highly configurable free version of the award-winning Bitdefender Antivirus

Bitdefender Free AV 2018

Runs on Windows 7/8/8.1/10 | Actively scans your system upon installation | Includes file scanner


  • Good malware detection performance
  • Low false positive rate


  • Lack of dedicated test results for free version
  • Requires Bitdefender account

Why we liked Bitdefender Antivirus Free Edition

Bitdefender’s free antivirus suite isn’t as feature-packed as its paid-for siblings, but it uses the same detection engine. Unfortunately, like Kaspersky and Avira’s free offerings, it’s not widely tested as a dedicated free product, which means we’ve had to rely on test results for other Bitdefender products that use the same malware detection engine.

After installation – a process that includes a threat scan of your system – you’re prompted to sign in or create a free Bitdefender account to use the software. In a change from our last test of the software, we weren’t able to open the antivirus interface until we’d done so.

Bitdefender’s main interface is deliberately and refreshingly simple. A simple window shows whether your protection is up-to-date or not, alongside a button starts a system scan. Unusually, there’s also a box you can drag files and folder into for instant checking, which is very reassuring if you suddenly spot an unexpected or unknown file on your system.

A settings menu gives you access to a log of events including scans, updates and detections, as well as  quarantined files, websites, files and directories that you wish to exclude from scanning – useful for software developers who don’t want their unfamiliar new files to be flagged as potential threats.

There are also options to disable Bitdefender Protection Shield real-time threat monitoring, which we don’t recommend, and, under Account info, to turn off pop-up adverts for Bitdefender’s paid-for products, which we do recommend.

Via your Bitdefender account, you get some basic online monitoring of your computer’s protection status and recent threads that the software has defended against. Bitdefender runs in silent mode by default, so it won’t interrupt you while gaming or watching films, and it doesn’t include any extra plugins or modules.

Bitdefender’s threat detection provides a good degree of malware protection, although its recent results from different testing firms have varied surprisingly widely.

The Bitdefender engine successfully defended against all threats in AV-Comparatives’ latest real-world threat tests. Over at AV-TEST, it defended against 100% of January’s real-world and reference malware sample tests, but its real-world performance dropped to 98.8% in February – a slight disappointment compared to the last tests we covered.

False positive detections of legitimate software were consistently low and Bitdefender had only a moderate impact on system performance compared to its rivals in both AV-TEST and AV-Comparatives’ performance tests, mostly when loading websites and downloading files.

Despite this, it’s apparent that Bitdefender Antivirus Free Edition is a solid choice for anyone after a simple and effective free protection tool.

  • Requires 2GHz Intel Core 2 Duo or better
  • 1.5GB RAM, 800MB free disk space


Get Bitdefender Free here

Proven to offer robust antivirus protection

Avira Free AV 2018

Works on Windows 7/8/8.1/10 | Can create bootable rescue disk | Optional free VPN


  • Good malware detection performance
  • Low false positive rate
  • Low impact on system load


  • No silent detection mode, so pop-up alerts will interrupt Netflix, games, etc

Why we liked Avira Free Antivirus 2019

Avira Free Antivirus 2019 is clean and simple bit of software, although we were surprised at its relatively high impact in AV-Comparatives’ latest performance tests, which found significant slowdown when it came to downloading files from the web.

However, the core application is efficiently designed. Rather than jamming loads of default features into its client, Avira presents a number of optional extras that you can choose to add at install time or after installing, including a network scanner, a free 500MB-per-month VPN service and system optimisation tools.

Avira’s interface is clean and surprisingly compact. It opens on a tab that displays your protection status, which modules are active, plus a couple of adverts for the Avira’s other products.

As this is the free version of Avira, some modules are marked as Pro only. You get its core real-time protection module, but not Antivirus Pro’s dedicated Web Protection and Mail Protection tools. Its firewall settings plug directly into Windows’s integrated firewall and are pleasingly easy to use.

You can run a variety of full, custom and predefined scans on active processes, local and removable media, but everything is kept simple by design, so there aren’t a lot of other options cluttering the place up.

Quarantine and Activity tabs show you what the program has been up to, while Avira’s advanced settings allow you to tweak the behaviour and sensitivity of the scanner, add processes and files you’d like to exclude, and disable audio alerts.

Avira Antivirus Free uses the same detection engine as its paid-for siblings, which we’ve referred to for test data.

Avira’s engine put in one of just a few perfect protection performances in AV-Comparatives’ most recent test real-world tests, with 100% of malware blocked and no false positives. A separate, more in-depth false alarm test came up with just 4 misidentifications – a good result.

AV-TEST also found that Avira protected with 100% accuracy in both real-world and reference malware exposure test, without any false positives, but found that its impact on system performance had worsened slightly compared to previous tests.

  • 1GHz Intel Pentium 4 or better
  • 1GB RAM
  • 2GB free disk space


Get Avira Free Antivirus here

Clear data collection policy with easy opt out

Avast Free AV 2018

Email scanning module | Can create bootable rescue disk | Windows XP SP2/Vista/7 SP1/8/8.1/10


  • Effective detection of drive-by download malware
  • Pop-up free silent detection mode
  • Clear, modern interface


  • Higher false positive incidence than some rivals
  • Default install options include software you may not want

Why we liked the Avast Free Antivirus

Avast’s free anti-malware suite is comprehensive and generally performs well. It shares its underlying detection engine with AVG, which Avast bought in 2016. However, the clients are different and we occasionally see minor performance differences in tests, usually dependent on the way each program requests user interaction when threats are detected.

In Avast’s case, it’s very important to always opt to view custom settings during installation and setup. Specifically, you’ll want to opt out of the Avast SafePrice price comparison browser extension and prevent the Avast Secure Browser from taking over as your PC’s default web browser and launching automatically at login, unless you really want that to happen.

The default installation options also include a rather more helpful Online Security plugin for other browsers, which scans websites for malware and blocks ad trackers, and a built-in password manager, although we recommend using a dedicated tool for that.

Avast is refreshingly upfront about its data collection policy – antivirus software typically collects information on its users’ habits and malware exposure as a matter of course – and clearly tells you how to opt out.

The software has a clean interface that follows Windows 10’s Modern UI style, with a main screen that shows your protection status and a one-button smart scan feature. Other features are available in the client’s Protection, Privacy and Performance tabs.

As you’d expect, you can run a variety of full and partial virus scans; view previously detected viruses; enable and disable Avast’s automatic file, web and mail scanning; scan your network for potential vulnerabilities, and create a rescue disk in case malware prevents your system from booting correctly at any point.

Avast has both a Do Not Disturb feature, which will prevent pop-ups when specified programs are running in full-screen mode, and its usual Silent mode, which prevents it from ever showing any pop-ups.

The program has a free, automatically renewing licence, and you can optionally connect it to an Avast account. The client shows unobtrusive adverts and extra feature buttons that promote the company’s paid-for products, which include a firewall, data shredder and system cleanup utility.

Avast’s advanced settings let you add URLs that you’d rather it never scan, have it scan for annoying-but-not-malicious unwanted programs, disable sound alerts and enable the program’s extra-paranoid Hardened mode.

Everyone tests Avast’s free antivirus product, which means that there are plenty of highly relevant test lab results to refer to. It detected 100% of AV-TEST’s real-world malware threats and reference samples over a two-month period, with just two false positive detections of legitimate software.

It also did well in AV-Comparatives’ real-world tests, defending against 99.7% of malware delivered online, but with a slightly disappointing 15 false positive detections. Alongside AVG, it’s almost the lowest-impact free antivirus suites available right now.

It’s a bit of a faff to install due to the potentially unwanted extensions it selects by default, and it came a little high on false positives, but Avast is certainly well equipped to defend your PC against threats, despite a few minor quality-of-life issues.

  • Requires Intel Pentium 4
  • AMD Athlon 64 or better
  • 256MB RAM
  • 2 GB free disk space


Get Avast Free Antivirus here

Includes built-in file shredder to destroy infected folders

AVG Free AV 2018

Email scanning module | Bootable rescue disk available as separate download | Windows XP SP3/Vista/7/8/8.1/10


  • Pop-up free silent detection mode
  • Effective detection of drive-by download malware


  • Higher false positive incidence than some rivals
  • Default install options include software you may not want

Why we liked AVG AntiVirus Free

Since 2016, AVG has been owned by Avast, and both use the same virus databases and detection engines. This is reflected in their very similar performances in testing, although there are minor differences to their default behaviour, particularly when requesting user interaction, which can make a critical difference.

Their performance in recent tests is virtually identical, but AVG lacks a couple of convenience features, such an integrated rescue disk creator. The AVG rescue disk, to be used in case malware renders your PC unbootable, is a separate download.

Like Avast, it’s a good idea to customise your options at install time, specifically to remove the SafePrice browser extension, which is a money-making price comparison tool that’ll pop up every time to try to shop for anything. You may also want to opt out of installing the AVG Secure Browser if you’re happy with your current browser security. If you do install it, be aware that its Express Settings will set it as your default browser and have it open automatically when you log in to your PC.

AVG AntiVirus’s grey and green interface gives you a quick overview showing your protection status, the time of your last scan and update, a quick scan button, plus a relatively unobtrusive advert for AVG’s paid-for Internet Security software and some inactive buttons showing features that you’ll get if you shell out for it.

AVG Free gives you critical real-time protection and scheduled and on-demand scanning, but the client also shows you which paid features you’re missing, such a firewall, encryption and anti-phishing tools. You can also optionally associate AVG with an online account and add extra paid-for features including a VPN and password manager if you want them.

Extra settings and options are available via a menu at the top right of the client, including access to your quarantined files and a file shredder to unrecoverably delete things .

You can enable a pop-up free silent mode if you’d rather not be bothered when your antivirus detects anything, disable email signatures marking emails sent from a desktop email client as scanned, and individually customise the sensitivity and behaviour of AVG’s email, web, software and real-time scanning components. You can also individually uninstall each of these components, but we wouldn’t recommend it.

We’ve included test results for AVG’s other products that use the same engine in our assessment of its performance results from major anti-malware test labs. During its most recent two-month test period, AV-TEST found that AVG products detected 100% of real-world malware attacks via the web and 100% of a large set of reference samples.

AV-Comparatives reports similar results, with AVG Free detecting 99.7% of real-world malware samples. However, it incorrectly detected 15 legitimate programs as malware in AV-Comparatives’ dedicated false positive test.

Like sibling Avast, AVG has a only small performance impact on most systems. However, we’d prefer it if both of them dispensed with the practices of automatically installing potentially unwanted browser extensions like SafePrice.

  • Requires Intel Pentium 1.5GHz or faster
  • 512MB RAM/1GB RAM (Windows Vista and above)
  • 1.2 GB free disk space


Get AVG Free Antivirus here

  1. Best overall: Kaspersky Free Antivirus 19
  2. Best built-in: Microsoft Windows Defender
  3. Best for configuration: Bitdefender Antivirus Free Edition
  4. Good performance: Avira Free Antivirus 2019
  5. Good comprehensiveness: Avast Free Antivirus

The key element of any antivirus software is its detection engine, which uses a combination of known signatures of malicious software and heuristic analysis of a program or file’s traits and behaviour to establish whether it’s potentially dangerous or not.

Detection engines are at the core of most antivirus companies’ business, and you’ll generally find that a company’s free products use the same engines as their paid-for versions. Paid products justify their cost with extra features such as firewalls and system optimisation tools

Modern antivirus software constantly monitors your PC and scans software, files and websites in real time to detect potential threats, but you can usually still run manual and scheduled scans for extra peace of mind.

Most AV programs run an optimised scan by default that checks the files most likely to have been compromised.

We’ve used test data on a per-engine basis, rather than an identical product basis, so, for example, we’ve used results from Kaspersky Internet Security to help draw conclusions about the Kaspersky Free, which uses the same engine.

The test data we’ve used was collected between January and May 2019, using the most up-to-date versions of the antivirus software available. AV-TEST carries out both real-world tests, in which systems are exposed to contaminated websites and emails, and reference set tests, in which several thousand malicious files collected in the previous four weeks are introduced to the system.

AV-Comparatives carries out a wide range of different, discrete tests. In this review, we’ve used the firm’s real-world test results, which involve live exposure to malicious websites that attempt drive-by downloads, as well as its dedicated false positive and performance tests.

In all cases, we’ve directly quoted the percentage or number of malware exposures successfully defended against in tests, as well as performance metrics and false positive test results, in which any blocking of benign software is noted.

It’s worth noting that there can be fairly dramatic performance differences from month to month. This depends on a given antivirus package’s ability to detect the malware that’s prevalent at any given point and the speed with which its signature database and heuristic detection rules are updated to reflect current malware.

AV-TEST and AV-Comparatives’ performance tests assess the impact of different antivirus suites on a number of common desktop tasks, such as downloading and installing applications, launching programs, copying files and visiting popular websites.

Related: Best VPN

While you don’t have to hand over any cash to use free antivirus software, its makers have to fund their business somehow. This manifests in a number of different ways. Some products, such as Avira, show unobtrusive adverts, while others are paid to bundle software and services from other vendors with their product’s installer or web browser plugins.

Any product that’s available in paid-for, as well as free, versions, will encourage to upgrade with varying degrees of persistence, with some including buttons for features that are only active for paid users in their main interface.

Many free AV providers encourage users to register for free accounts by providing online monitoring tools that you can use to manage and secure other devices associated with the same account, such as phones and tablets.

Our reviews detail any intrusive advertising or promotional features in each free AV suite and, where possible, tell you how to avoid them.

Antivirus software also, by default, reports back to its manufacturer when it encounters unknown malicious and even benign files. This data gathering is an important function of free antivirus suites as far as their creators are concerned.

In practice, it means that the malware databases the software relies on are kept constantly up to date, helping to protect all its users and making both paid-for and free versions more accurate.

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