It’s easy to forget that Nintendo 3DS is over 8 years old now, having launched in North America in March 2011. For a frame of reference, iPhone 4 was the latest Apple device at that time. I myself didn’t even have a smartphone yet, instead carrying around a flip phone with seemingly immortal battery life. So when apps like the YouTube app made their way to the 3DS, it was a charming novelty at the time.
These days, it’s a lot more likely you have more convenient ways to access YouTube, and that’s good because–the app might be broken on Nintendo 3DS. Reddit users are reporting an inability to view videos on the YouTube app, and one user has uploaded a video of receiving an error message when trying to watch videos.
A theory behind the video crashes (also from Reddit, of course) is that there has been a change in the API in how videos are fetched, because videos reportedly crash with a prefetch abort. In any case, it seems unlikely the problem will be fixed. This could be the end of the 3DS app.
However, if you desperately must watch videos on your 3DS, you can still apparently view YouTube videos through the internet browser on New Nintendo 3DS XL and 2DS XL. For now. *Grim Reaper laughs in the distance.*