Windows Defender has a market share of 50%

Martin Brinkmann
Aug 3, 2019
Updated • Aug 3, 2019

Microsoft integrated the security solution Windows Defender Antivirus deeply in the Windows operating system. It is enabled by default on the company's Windows 10 operating system so that it can protect devices from the moment they are booted for the first time.

Previously, systems did not really have protection until users decided to install antivirus solutions on devices.

Microsoft revealed recently that Windows Defender Antivirus has a share of more than 50% on Windows; the solution is the primary antivirus solution on more than 500 million Windows devices and growth continues.

The market share of Windows Defender Antivirus makes it a prime target for attacks that bypass its protections. If an attacker manages to find a way through the defenses offered by the security solution, a large part of Windows systems would be vulnerable as a consequence. Kaspersky called Microsoft out in 2016 stating that Microsoft's integration was anti-competitive.

Microsoft told ZDnet that it predicted that Windows Defender Antivirus would become a high priority target and that it invested in defensive mechanisms to improve protections. In Windows 10 version 1903, Windows Defender got a new anti-tamper protection feature, and it uses a sandbox since 2018.

The most recent test on AV-Test, an independent test site for security solutions, awarded Windows Defender Antivirus a perfect score. Microsoft's security program got the perfect score in protection, performance, and usability.

windows defender 500 million

Granted, it was not the only tool that received a perfect score in the test. Three third-party security solutions -- Norton Security, Kaspersky Internet Security, and F-Secure Safe -- managed to get a perfect score as well. Five additional security solutions got recommendations as well.

Windows Defender Antivirus may be the default security solution but it is designed to disable itself automatically when an administrator installs another security solution on a Windows machine.

No antivirus solution offers 100% protection against all threats; it is clear that Windows Defender has improved over the years. One of the program's main advantages is that it is deeply integrated in the operating system. Third-party developers face problems sometimes when Microsoft releases new versions of Windows.

Avast Antivirus users ran into issues frequently in recent time on Windows 10. In 2018, some reported that Windows would boot into a blank desktop after an upgrade, and in 2019, systems with Avast business solutions installed would become unresponsive after update installation. Other security solutions, e.g. by McAfee.

Closing Words

Windows Defender, which soon may be called Microsoft Defender, is getting better with every update. Is it enough? What is your take on the development? (via Deskmodder)

Windows Defender has a market share of 50%
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Windows Defender has a market share of 50%
Microsoft revealed in August 2019 that Windows Defender Antivirus has a market share of more than 50% on Windows and is installed on more than 500 million devices.
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  1. Ehab said on September 8, 2020 at 7:55 am

    after update windows go to Bullguard internet security

  2. Niko said on August 5, 2019 at 10:12 am

    Microsoft Defender? Just try to start Portable Apps menu with 50+ applications listed… and meanwhile go and make some coffee, wash your car…, take kids to movie…

  3. ULBoom said on August 5, 2019 at 12:20 am

    I guess MS decided to focus on Defender given they capitulated to Google in the browser wars and Google’s android AV is possibly the worst on the planet.

    Now that Defender works OK (AV test results vary month to month and Defender came in dead last, far worse than any others, in false positives in the tests mentioned here), MS can vacuum user data with both Chromedgium and Defender.

    No reason for the mass of users to go to third party browsers or AV’s. They can just hope they don’t get really hosed by Windows Update.

    Putting all your eggs in one basket, sending all your data to one company, aren’t safe strategies. Of course MS is going to make all this look fabulous, let’s see if it is over time, they’re proven experts at wrecking Windows.

  4. o_O said on August 4, 2019 at 8:49 pm

    No need to install third party antivirus, at least something microsoft is doing right, providing a free built-in antivirus with basic protection that is good enough. Installing ublock origin and virustotal will solve the rest.

  5. jern said on August 4, 2019 at 4:13 pm


    You write…
    “Microsoft revealed recently that Windows Defender Antivirus has a share of more than 50% on Windows…”

    Does that cover just Win10 or does the statistic cover the entire Windows world? As of July 2019, Win10 use was at 58.59% while Win7 had dropped to 31.24% with other versions stringing along behind.

    Worldwide, Windows use has dropped to 35.06% compared to Android at 39.97%.

    1. Martin Brinkmann said on August 4, 2019 at 8:41 pm

      Microsoft did not mention that; I’d assume it covers all Windows versions but that is just my guess.

  6. Anders said on August 4, 2019 at 9:38 am

    From a performance perspective it is horrible. I do not see how it can score high in that metric. In particular the live protection makes certain workflows nearly impossible, anything involving processing many of large files. You will often see disk performance degrade by up to 10 times. If you are working as a developer or processing media files this is very frustrating and you will see a huge chunk of your day go up in smoke.
    There are high quality competitors that are not nearly as demanding.

    1. John G. said on August 4, 2019 at 6:23 pm

      Completely agree! Disk usage by Defender is absolutely insane in certain moments! Online gaming becomes a nightmare when it starts to scan everything or whatever it does on the disk!

  7. Sebas said on August 4, 2019 at 9:23 am

    Windows Defender on my desktop uses few resources, and sits quietly at the background. Sometimes I would like to replace it with Kaspersky internet protection (the paid version), which I found excellent on Windows 7. But the chance of problems with every Windows update is too high for me. It is quite heavy too.

    The only annoying thing is the ransomware protection component. For me it is confusing, so far only giving warnings for legitimate programs. So I disabled it. Frequently backing up files is the best protection against ransomware anyway.

    Apart from that it is a competent AV. I do hope they add Windows sandbox to the home edition.

  8. Pratha Scullion said on August 4, 2019 at 6:11 am

    I agree with Martin Brinkmann and many of the comments posted here — Windows Defender has turned-out to be a pleasant surprise.I used to have Avast and uninstalled it after they started putting their logo on the e-mails I send out — that is something I simply will not tolerate.As I said,Windows Defender has been a pleasant surprise.I really didn’t think it would work as good as it has,but given time,it has shown me otherwise.While it’s not the only anti-virus protection I have,it has certainly worked well enough to keep it.The fact that Microsoft keeps it updated is a big plus and shows that they are committed to it.So far,I’m happy with it!

    1. Declan said on August 9, 2019 at 6:43 pm

      Pratha … you can turn off the Avast email signature inside the Settings section.

  9. The Seeker said on August 4, 2019 at 1:42 am

    “…and it uses a sandbox since 2018.” This still has to be manually enabled, right?

  10. Lambo-san said on August 3, 2019 at 7:53 pm

    I have disabled Defender and I don’t have an antivirus bloatware installed either, it’s a complete waste.

    1. John G. said on August 4, 2019 at 11:42 am

      On low computers, it’s better any lightweight antivirus than Defender, it eats all CPU for long time!

  11. dark said on August 3, 2019 at 6:40 pm

    Market share achieved by forcing it on users computers.

  12. Robert Ab said on August 3, 2019 at 6:07 pm

    Windows Defender or Microsoft Defender? I have read that Microsoft changed its name from Windows Defender to Microsoft Defender.

    1. Martin Brinkmann said on August 3, 2019 at 6:21 pm

      Microsoft Defender from 20H1 onward, Windows Defender currently. Could change though, one never knows.

  13. Clairvaux said on August 3, 2019 at 4:22 pm

    How different is this from Microsoft Security Essentials ?

  14. JohnIL said on August 3, 2019 at 4:03 pm

    Works well for me, and the integration with Windows 10 means its going to work even through updates and feature upgrades. I am convinced even more now that security test give it high marks for protection.

  15. Marcello Solara said on August 3, 2019 at 3:47 pm

    I don’t trust any AV besides Microsoft’s. Too much spyware adware junk that’s difficult to remove from your computer

    1. Anonymous said on August 3, 2019 at 6:06 pm

      well i dont trust microsoft. Windows 10 itself is spyware and adware(start menu ad & stuff)…pretty sure a few month back there a case where windows 10 user got served with malware ads in start menu

      1. Marcello Solara said on August 3, 2019 at 7:21 pm

        I don’t disagree, nonetheless I think MS’s AV itself isn’t adware, unlike most popular AVs

  16. obwieÅ› said on August 3, 2019 at 1:46 pm

    Sure, perfect… Last month I received an email with a virus attached. Almost all Virustotal agents identified it 100% virus, except Defender. I submitted the sample to the Defender team at Microsoft via dedicated webpage and a second time from another machine then had to wait 2 more weeks for Defender to recognize the malware…

  17. Paul(us) said on August 3, 2019 at 1:10 pm

    That’s a real great development this because there are probably more than 100 million people who still not now that its smart to install a antivirus solution.

    But what is really puzzling me about this article Martin is that you (and deskmodder) are writhing that there are 5 outer additional recommendations giving software, are those also perfect score anti-virus applications and who are those?

    Next to that are there in the testing also antivirus software with a firewall included?
    And is it way smarter to have installed antivirus software with a firewall included?
    This because than maybe those two security measures are than better working together?

  18. chesscanoe said on August 3, 2019 at 1:00 pm

    As I have indicated in prior comments, I am glad to see Windows Security, as it is called when hovering over its notification icon, is getting the favorable press it deserves.

  19. Ascrod said on August 3, 2019 at 12:11 pm

    Not sure who I trust less – Microsoft, or 3rd parties vendors. At least Microsoft’s business model isn’t based on scare tactics.

    1. ilev said on August 3, 2019 at 7:12 pm

      I hope your are joking. Microsoft business IS build on scare tactics , extortion, intimidation, bulling, bribes, harvesting and selling privacy data..
      Microsoft in business in no better than Cosa Nostra..

      1. Gwstas said on August 4, 2019 at 6:45 am

        Haha you’re delusional. Just don’t use a PC and you’re gg.

  20. Yuliya said on August 3, 2019 at 11:22 am

    If you really need an a/v, MSE/WD is the way to go imo. It is annoying however that they know ths stat, which a/v software the user installs. But then again MS revealed a few years ago how many pictures, and how many hours of videos the users watched using windows 10…

  21. Darren said on August 3, 2019 at 10:43 am

    Who’s watching the watchers?

    1. SatanNečastivi said on August 3, 2019 at 11:32 am


      1. pndy said on August 3, 2019 at 6:43 pm

        You mean Roumburak, SatanNečastivi, right?

  22. Dan said on August 3, 2019 at 9:02 am

    Market share of Windows Defender would not be 20% if it was not built into windows. Just another tool used by Microsoft to collect user information. I would say 25% benefit to user and 75% data collection from user.

    1. Herman Cost said on August 3, 2019 at 3:21 pm

      With a couple of notification tweaks, Defender works quietly and effectively in the background without making a PITA of itself. Compare it to something like Avast and its clear that Microsoft has for once done a good job here for its users. Now if they would only junk the whole Windows as a service concept and let actually people have control over their own computers. Okay, okay, I won’t get carried away.

    2. Shiva said on August 3, 2019 at 12:40 pm

      Well, in this case the situation is not the best between all the competitors (free or not). The issue is that with Internet Securitty programs you obviously can’t block them with Firewall otherwise you don’t receive the daily updates. Anyway, looking at Kaspersky data provision you can see a ‘little’ difference based on GPRD:
      I suppose (but I’m not holding my breath) that GPRD been has very clearly reflected in Windows 10 and Windows Defender. The last AV report about data transmission was in 2014:

    3. Major said on August 3, 2019 at 11:51 am

      So, you’d rather provide your data to russia via kaspersky?

      1. Robert said on August 3, 2019 at 3:45 pm

        No way. I’d rather let the American government spy on me because we trust them.

  23. seeprime said on August 3, 2019 at 8:43 am

    I give credit to Microsoft for making Windows Defender so effective, such that third party AV’s aren’t needed unless one has a personal preference for one.

  24. Anonymous said on August 3, 2019 at 8:28 am

    TYPO your spell checker missed:
    Microsoft’s security program got the perfect SORE in protection, performance, and usability.

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