Is a DeepL account private?

As mentioned in Translation software/services:

I use DeepL, but it seems to be going downhill a bit. I’m not sure how private it still is, but, for example, it now only lets you translate 1500 characters instead of 5000. And their mobile app, which is the only place you can do image translation, is of course non-free.

In addition to those problems though, they’re also trying really hard to push an account on your. For example, they won’t let you translate documents without one.

Is this account private (if DeepL is even private in the first place)? As in, can I create one and be safe in the knowledge that am I not giving up my privacy?

Well the data is transmitted to their servers in any case, whether you use it with an account or not. What happens afterwards, there is no way for us to know and therefore, as with any translation service offered by someone over the internet that runs on their servers, it is not strictly private.

If you think that you trust them in general as an entity, only then it might be relevant to look into what they claim they do with your data. In that case you would need to look at DeepL Privacy Policy | Protecting Your Privacy Is Important To Us and there you see that whether you use an account or not, if you’re not a Pro subscriber, they will use input data to train their models and they also explicitly forbid you to translate any texts containing personal information (presumably because that information is not gonna be sufficiently protected). They do however claim that if you’re using their paid Pro account services, then they will make sure your input data is not stored in any way after translation. But again, whether that is actually the case or not, that is another story. I don’t see any reasons to not trust them, but I also don’t see any reasons to trust them.

Actually private translation would need to happen on your own devices without your input data being sent to someone else’s device first.