Jane included a video in her tweet, which she claimed was produced in collaboration with Facebook, to show the new feature
Several users responded to her tweet, claiming they've been using this feature for a while, some as early as August.
Facebook did not clarify when it would initiate a full roll out.
To find out if you have the feature, check for Dark Mode in the app’s Settings and Privacy option.
If you do, you can turn it on or off, or make it default to your phone setting.
Wong discovered Facebook working on the feature last year and correctly predicted that it would take some time to be introduced due to the size and complexity of the Facebook app.
The Facebook app will be one of the last to receive dark mode, as the desktop version and Messenger app, as well as Facebook-owned apps like Instagram and WhatsApp introduced the feature much earlier.