It's fairly rare during general browsing, but Mullvad makes no attempt to hide that their servers are VPN IPs, so any site that explicitly wants to block VPN users will very likely block Mullvad. Mostly an issue if you're trying to use a VPN to view geo-blocked media.

I get lots of Cloudflare authenticators, some Youtube content gets blocked, and a few sites will not load at all. Reddit (which I avoid as often as possible) blocks it completely [1]. Switching to a different country sometimes works but increasingly does not. I don't use streaming services apart from Youtube.

Still, I am happy with the service and will continue to use it.

Edit:

[1] As others have written below, Reddit blocks when not logged in. Since I don't have an account, that's a 100% block rate for me.

Often enough.

Some Mullvad locations will cause Google to throw up excessive captchas. Others will cause reddit and imgur to 403 your response.

For most places, not a problem, but some WAFs are explicitely blocking certain known IPs.

EU user here. Streaming platforms approaching 100%. Other than that, not common, but slightly increasing.

Often. It is becoming a big problem. In the last couple of days youtube has become almost unusable. Reddit is usually blocked. Twitch shadowbans chats. A lot of random unexpected sites block it like wiki pages. Captchas make google too annoying to use (but mullvad has its own proxy called Leta but it lacks features like suggested corrections to the search). I still use it always and persist despite this. Often hopping servers will work but I might have to try 5+ different servers

I switched from Mullvad to ProtonVPN for this exact reason about 1.5 years ago. Unfortunately ProtonVPN seems to be even worse at this now. It's become clear that the more popular VPN services are increasingly having connectivity problems to many popular sites (social media, streaming media, etc.)

Often if you're on a bad node that has been rate-limited, usually connecting to a different node in the region helps. However VPN blocking very often and more frequent especially this year, it seems like walls are going up everywhere.

Side note: one of Mullvad's Miami servers is blocked by HN, I have to switch nodes if I land on that one because "Sorry" message.

I use the default endpoint in Sweden, and I can’t access Reddit and YouTube without being logged in (which I refuse to do). Not an issue in the end because it’s mostly a waste of time.

It's highly dependent on the endpoint selection. Some providers' IP ranges are blocked while some are not.

In my experience it happens, but rarely. Fairly often I get captchas which is annoying, but tolerable.

Most Cloudflare sites throw up captchas, switching to other Mullvad servers every hour does not help anymore. Reddit blocks completely. Many other YC funded startups block Mullvad VPN (I miss Paul Graham's influence, don't you?). Port forwarding was removed by Mulled company so less bittorrent peers. All magnet link search engines and 90% torrent sites block Mullvad, even though these sites advertise VPN.

Enshittification is nearly ubiquitous now [1].

[1] https://en.wikipedia.org/wiki/Enshittification

Reddit blocks it. Very annoying.

Edit: when not logged in.