Mozilla has announced
the release of a translation plugin for Firefox as part of the Project Bergamot initiative.

The ultimate goal of this consortium was to build a set of neural
machine translation tools that would enable Mozilla to develop a
website translation add-on that operates locally, i.e. the engines,
language models and in-page translation algorithms would need to
reside and be executed entirely in the user’s computer, so none of
the data would be sent to the cloud, making it entirely private.

Source: LWN.net – Mozilla releases a machine-translation plugin