Greetings,
The draft designs for how multilingual file captions may work on the file page is up on Commons. [1] Feedback is welcome on the talk page, as well as any relevant questions. [2]
Multilingual captions were first introduced back in January as a proposed change to the UploadWizard, [3] and will be one of the first features of structured data on Commons later this year.
Thanks, and as always I invite you to follow along with Structured Data [4].
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Keegan Peterzell
Technical Collaboration Specialist
Wikimedia Foundation