The Safari web extension is bundled with the Translatium desktop app available on the Mac App Store.

Enable the Extension

Before enabling the Safari Web Extension, run the Translatium desktop app available on the Mac App Store (version 19.4.0 or higher) at least once. In Safari:

  1. Open the Preferences window. (from the menu bar, select Safari > Preferences...)
  2. Navigate to the Extensions page.
  3. Check the Translatium with Translatium checkbox, and select Turn on in the confirmation dialog.
  4. Give permission for the extension to run on every websites by select Always Allow on Every Website..., and then select Always Allow on Every Website in the confirmation dialog.

The extension is free, open-source and does read or alter the websites you visit, or collects data from you.