Translate Web Pages does not collect any data.
The only communication is with Google (translate.google.com and translate.googleapis.com) and Yandex (translate.yandex.net) server.
To detect the language of the page on mobile devices, 600 characters are sent to Google.
To translate, all content on the page is sent to Google or Yandex servers.
The source code is available on Github.
If you choose to use Google and Yandex widgets instead of my algorithm. These widgets can collect various data.