Video consumption on mobile has exploded over the last few years. Now creators have diverse audiences tuning in from all kinds of devices including phones, PCs, and even TVs. Previously, some portion of the audience would suffer with content that didn’t really fit their screen orientation or device usage, but no longer! We’ve developed a solution built on client side encoding and multitrack ERTMP so broadcasters can contribute synchronized horizontal and vertical content — and we’re not just talking about simply ripping a vertical slice from the main horizontal content. Creators can thoughtfully design their content and layout for both formats to reach viewers anywhere. In this talk we’ll show how broadcasters can contribute dual format content and how we deliver it to viewers, including new HLS multivariant playlist functionality we designed to overcome standards limitations that got in the way of a synchronized, adaptive playback experience. This talk was presented at Demuxed 2025 in London, a conference by and for engineers working in video. Every year we host a conference with lots of great new talks like this – learn more at https://demuxed.com