1- Did you wonder if Avast has the largest database of Windows Defender than Microsoft?
2- Since Microsoft is installed around the world, I understand that the largest database is hers, because of collecting threats with great volume.
3- Microsoft it uses several servers to do analysis, according to the link that I will put below.
https://www.youtube.com/watch?v=ps9ntazo1v0
4 - The work this man who is speaking in the video and great, he has Microsoft’s MVP, with what he says has a lot of basis in what it says about security.
5. Did Windows Defender become the safest for reasons he explained?
→ https://forum.avast.com/index.php?topic=217477.0
PS: Most of us don’t speak your language, so we can’t comment the video.
Hi Asyn, this vid we can all understand, it is visual : https://www.youtube.com/watch?v=KHKHZnH9bm8
polonus
Hi Pol, personally IDC about such videos (esp. outdated ones from 2016 ;)).
Heres a newer video: https://www.youtube.com/watch?v=tFiw8JQxyO4
Size is an imponderable and not something that you can use as a definitive answer to who has the most or best database.
Avast is constantly optimising its database, tweaking signatures to detect more than a single virus signature.
If there was a single detection signature for every piece of malware, the database file size would be massive. This would make it pretty unwieldy and slow.
I would also add, that regardless of size of data base for known virus’ (whoever has the larger) malware detection is very much now more about Heuristics, AI and Behavior analysis/detection components.
Thanks for the clarification on the subject of the virus database.
You’re welcome.
One should also take in consideration PUP detection and blocking suspicious destinations like PHISHING sites,
just there where cybercriminal activities lure.
Windows Defender does not equal normal AV in these respects nor even has Google Safebrowsing grade protection.
See Pondus’s response on this matter. So Windows Defender is even catching up here. 
Of course one adds a good ad- and script blocker to the browser like uBlock Origin and uMatrix,
or MBAM alerts for certain content alerts.
Moreover I write this post inside the Avast Secure Browser and there is a reason for that too.
Windows Defender is not bad for the moments that your AV for one reason or another does not work,
for instance because of critical Window file’s FPs, but not under normal conditions.
polonus
Microsoft SmartScreen >>> https://en.wikipedia.org/wiki/Microsoft_SmartScreen
Hi Pondus,
Thanks for given the latest information on this. Apart from this, what is the actual difference between Windows Defender and free AV?
Is it heuristics or can they be compared on an equal basis?
polonus
If you check AV compare they are doing very good
AV Compare >> https://www.av-comparatives.org/
The thing i saw is that avast setup often freeze windows defender and launching.
You have to turn it on after.
It is normal for resident avast AV to disable some of the functionality of Windows Defender.
But be prepared for all eventualities.
Two resident av-solutions won’t and cannot work together,
It is just like having two mean dogs in from of the parlor for better protection.
They are going after each other in stead of after the threats you may have in the form of malcode.
Turn Windows Defender full on if for some reason or other your avast solution won’t function properly.
We have come across such incidents rarely in the past years.
For instance the mishap that avast will FP files critical for windows to function properly.
Only in such cases it is a good thing to disable avast resident for a while,
and to let Windows Defender temporarily come back to do the job.
When avast comes out of such mishaps and sounds the all green again,
bring up your old av solution of choice again.
polonus
It isn’t Avast that disables Defender. Defender shuts most of itself down when a third party AV like Avast is installed. 
Hi bob3160,
OK, when Windows Defender is the initiator there, whener it finds out about you running a resident AV solution of sorts.
On the other hand, would not it be great to have a fall-back to Windows Defender mechanism
under such rare occasions when your resident AV meets with an emergency update,
that FPs and so breaks critical Windows files, so you cannot run to use your computer any longer.
Under such circumstances a fall-back to disabling the resident AV and bringing Windows Defender full strength back up again,
until your AV misery has been settled by a new update, would be a welcome emergency scenario.
Cannot they bring that in.
We had such a tragic scenario twice in the past and some thanked Gd they missed such updates,
(DavidR for instance and little old me at the time), because they had not touched their device and missed that bad update,
and so never met the scrwed-up definitions and situation. ;D
polonus
Sorry Dameon but I don’t know what question you are asking or if it is actually a question.
I simple corrected your statement as to what turns of what.
Hi bob3160,
Rightly so. Thanks. I and that issue stand corrected.
My additional question was if Defender shuts itself down when experiencing a resident AV solution,
cannot it come back up again when the resident AV through a False Positive on critical OS files for instance wrecks the Windows OS.
Would be a handy feature for such circumstances and in the meantime we could wait for safe and secure updates.
Should this be addressed to Microsoft or to avast?
Damian
Should be addressed to both.
If Avast would totally shut down when there is a problem, Defender would turn itself back on.
When there is only a part of Avast that’s no longer working or, if Avast isn’t up to date,
Defender issues a warning only but doesn’t start up.