Level 32
Twitter today announced it will begin testing a feature with a small group of users that automatically translates tweets that are in a language they may not be able to read.

Currently, users whose primary language is set to English in Twitter can tap or click a button to manually translate a tweet in their feed that's in another language.

Starting today, however, users in Brazil will see English-language tweets that have been automatically translated to Brazilian Portuguese, rather than having to manually opt to translate it themselves.

Twitter explained the pilot test in a blog post:
In order to make it easier to understand the conversations you follow on Twitter, we are experimenting automatic translations to Tweets in other languages that appear on your home page. We know that sometimes it can take a long time to translate Tweet by Tweet and stay on top of what is relevant to you.
Twitter says that one part of the testing group will see the translated text and can click to return it to the original language, while the other part will view the translation and the original text in the same tweet in a standard way. If a tweet is translated, it will be accompanied by the warning, "Translated from English by Google" or "Translated from English by Microsoft."