Virustotal

Let's you upload any file and it will be scanned with pretty much every virus scanner software out there, which is over 60 of them.

This obviously can't replace having antivirus software on your computer because it only scans individual files, but it's great to use if you come across something suspicious.

Like a file that you downloaded and your antivirus software says it's fine, but you want to be sure.

Or maybe your antivirus says it's a virus but you think it could be a false alarm.

In both cases you can use Virustotal to compare it to all the other antiviruses to get a better idea.

It even has a feature to check links as well so if someone sends you a suspicious link, I highly suggest to scan first on Virustotal. It's convenient and free to use so go ahead and try it.