Sometimes it may look like our service is out of shape or not working properly, due to stuff happening on your computer. Here's some background information as to why this may be happening to you.
Antivirus software can be like an overprotective parent; intentions are great but sometimes they just get it all wrong. If that happens, your antivirus software will cause problems with both uploads and downloads on WeTransfer, because the software doesn't trust us. Our service will be actively blocked from connecting with your computer.
The great thing about antivirus software though is that it updates quite often. Updates will add newly found viruses and tweak the software, which may have a positive effect on how well our service performs in combination with the antivirus software. That's why we ask you to check if your antivirus software is up to date (not all antivirus software automatically updates, and we can't see what kind you are using) before moving on to other suggestions such as adding our domains to your trusted websites.
Some software uses a web shield (Avast, for example) which we know can block our service, others such as ESET use HTTP checking, and even others such as Bitdefender just seem to completely disable our service.
Something completely different but with the same result (our service not working properly) are browser extensions or plugins. Flash blockers for example, block parts of our interface, which renders it useless. Ad blockers can detect advertisements, but sometimes also disable parts of our interface if they interpret parts of the code incorrectly.
As you might suspect by now, the cause of slow connection speeds is usually not WeTransfer itself but rather the way it's being blocked, slowed, throttled and disabled by different third party apps.
We test all of our service for all major browsers, but not in combination with other apps. The reason for this is that we simply can't test for all possible combination of software on individual users' computers. We know that certain antivirus apps interfere with our app, but because they change all the time (updates, new features) we can't pinpoint the exact cause in many cases.
We can't write our service to work around antivirus software, because that's exactly what antivirus software is for: to defend your computer from unwanted software accessing it. Sometimes it just works too well, just think back to the overprotective parent comparison we made at the start of this article.