In June 2026 Twitch let every streamer send a vertical feed alongside the usual one. Since August, YouTube has taken a vertical feed from your encoder on a second stream key. Whatnot’s OBS guide now talks about its “new 1080x1920 9:16 vertical resolution canvas”. If you stream from a PC, vertical stopped being a separate project this year and became a second output of the stream you already run.
This post is the state of play, platform by platform, as each platform’s own pages described it on 20 October 2026. Then it covers the part most setup guides skip: what a second shape does to the overlay on top of the video. We make an overlay tool, so we have an interest. The sources are listed at the end, and where a fact comes from a third party rather than the platform, the text says so.
Why this year
Two numbers explain the rush. When Twitch launched Dual Format, it wrote that “70% of new viewers are coming to Twitch on mobile.” And in the first quarter of 2025, by Streams Charts’ count as reported by Tubefilter, TikTok LIVE drew about 8.0 billion hours of watch time against Twitch’s 4.8 billion. That second figure is eighteen months old and measures something different from Twitch’s, but both point the same way: a large share of live viewing now happens on a phone held upright.
Streamers were building vertical feeds before any platform asked for one. Aitum Vertical, a free OBS plugin that adds a second, vertical canvas with its own scenes, shows over a million downloads on the OBS forum.
Twitch Dual Format
Twitch has offered Dual Format to all streamers since 17 June 2026. One broadcast carries a 16:9 feed and a 9:16 feed. Mobile viewers see the vertical view by default and can tap to switch to the classic split view, and rotating the phone gives them the full-screen horizontal picture. What Twitch’s help page asks for:
- Enhanced Broadcasting, always, even if you have server-side transcode support.
- OBS 32 or newer with the latest Aitum Vertical (1.6.6 on 20 October 2026) or StreamElements’ SE.Live as the additional canvas. Streamlabs, XSplit, Meld and Streamrun are also on Twitch’s list. StreamElements warns that running SE.Live and Aitum Vertical together can crash OBS, so pick one.
- A vertical canvas of 1080×1920. You press the normal Start Streaming button; there is no second go-live and no second stream key to manage.
- Upload of 12.5 Mbps at 1080p with server-side transcode, which Twitch provides for Partners and select Affiliates, or 13.5 Mbps without it, on Windows 10 or 11 only.
Two details matter for anything you put on screen. Twitch draws chat over the vertical video, and viewers can tap to show more, less or none of it. Twitch’s own advice is to “keep important visuals in the center safe zone” and to skip a chat overlay of your own, because it adds chat to the vertical view for you. Also worth knowing: the vertical version of a VOD expires seven days after the stream, and Dual Format isn’t available yet if you go live from the Twitch mobile app.
YouTube’s dual stream
YouTube live streams go out in both shapes by default. The catch is how the vertical one is made. In YouTube’s words, “The vertical stream is a center crop of the horizontal stream.” Anything in the corners of a 16:9 frame, which is where most overlays live, falls outside that crop.
Since August 2026 you can send your own vertical feed instead. In the Stream tab, the vertical preview has an Auto dropdown with an Encoder option, which asks for a second stream key over RTMP(S). Set it up before you start: YouTube says you can’t add the vertical format once the stream has started.
Be clear about who sees it. YouTube says viewers watching in the Shorts feed on mobile see the vertical version, and “all other viewers will see the horizontal stream.” That is not every phone viewer. The vertical feed also has no clickable links in chat or the description, no live ads, no Premieres, no live redirect and no 4K on the YouTube app. In exchange it is the only one of the two that can be discovered in the Shorts feed. Live chat is shared across both.
TikTok LIVE Studio
TikTok LIVE is vertical, and from a PC the usual route is LIVE Studio, TikTok’s desktop app. The only threshold we found in TikTok’s own text is age: you must be 18 or older to go LIVE. Third-party guides list follower and account-age requirements and add that they vary by region, so what your app shows is the answer.
To bring an overlay in, vendor guides describe a Link source that loads a web page, where you can set a size such as 1080×1920 if LIVE Studio offers one. Some streamers report Link sources that load blank or stop updating on long streams. The usual fallback is to build the scene in OBS and send it to LIVE Studio as a virtual camera, though one guide says new LIVE Studio accounts can use virtual cameras only after three LIVE Studio streams of 25 minutes or more.
The rules matter as much as the layout. TikTok’s Community Guidelines, in force since 24 September 2026, make LIVE creators responsible for third-party tools, and they name “on-screen comment displays”, which is what an overlay is. Under “Trade” they list giveaways and “directing people off-platform”, which includes posting links. TikTok’s text never says “QR code”, but in our reading a code that sends viewers to another site is a link by another name.
Whatnot
Whatnot sellers can stream from OBS, and the setup is strict. The canvas has to be 1080×1920: Whatnot’s Health Check pop-up treats 1920×1080 as incorrect. It streams over WHIP rather than RTMP, the bearer token changes with every scheduled show instead of being a fixed stream key, and the required output settings are applied by the Show Tools websocket, for which Google Chrome is the only supported browser.
What this means for your overlay
Put the four together and a pattern shows. Every platform now wants a 9:16 frame, and every one draws its own interface over it: chat across the lower part on Twitch, comments and buttons on TikTok, comments on YouTube’s vertical feed. An overlay laid out for 16:9 has two bad outcomes in that frame. Squeezed to fit, its text becomes tiny. Cropped, its corners vanish.
The common answers are a second set of art drawn for 9:16, or a second set of scenes with everything moved by hand. Both work, and both leave you keeping two layouts in step. We compare them fairly in a separate post, and another goes through why a 16:9 overlay looks wrong on a phone in detail.
16:9 · 1920×1080
9:16
One overlay link in two frames. Press a key and it plays in both.
What it does not do: Kloot fires when you or a mod press a key. It never reads gifts, subs or chat on any platform. Under the TikTok profile, the giveaway card drops its QR code and join link and shows a “free entry” card instead, because of that Trade rule. Kloot doesn’t read TikTok chat, so viewers on TikTok cannot enter from the screen today, and the panel tells you so.
Where to start
If you stream to Twitch from OBS, Dual Format is the cheapest test: one plugin, one checkbox, the same Start button, and a vertical VOD you can check for a week. If YouTube is home, encoder mode gives you a proper vertical feed instead of a crop, but weigh the missing links and ads on that feed. If your audience is on TikTok, LIVE Studio is the path, with the virtual camera as your backup. And if you sell on Whatnot, set the 1080×1920 canvas first, because nothing else matters until the Health Check passes.