Android- ads in applications are in local language even when using proxy

Question

I have noticed some weird behavior on my smartphone that I can't explain myself.

I'm using Orbot application as proxy to route all of the phone's internet traffic through the Tor network.

When I search through browser "my ip" websites, results show Tor.

On the other hand, when I use other applications, ads in them are in my local language (very small number of speakers). I've noticed this mainly in ads in websites while browsing (Google browser and DuckDuckGo browser). Or when application is just wrapper of some website and again this website shows ad in my language (all websites are foreign). I think I have registered this in some non web browser applications on bottom where ads tend to be but not certain.

1 Sorry for adding this into comment, posted question as a guest...

Phone has set language as English and "region" is also different country

I've used phone originally for some time without proxy. Is it possible this is because of this and some identifying numbers of phone?

Google services do not have internet access. Permissions of these applications seems to be fine.

Answer 1

Tor only hides your IP address. It does not hide metadata sent in HTTP(S) requests. For example, it will not remove tracking cookies, it will not prevent the webRTC protocol to leak your original IP address, and as commented by Steffen Ullrich it will not remove the HTTP Accept-Language header.

That's why the Tor Project recommends strongly to use the Tor Browser which has built-in protections to prevent the user to expose his identity.

But even using the Tor Browser, the users must force themselves to use strong operational security to avoid leaks. Operational security means building and only using a fake ID when using the Tor Browser, never using this fake ID outside this browser, and never revealing identifying information when using the Tor Browser.