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To stream vertical video to YouTube with Castr, send a source into Castr, add YouTube as a destination, and configure YouTube’s vertical live stream before you go live. Castr handles ingest and forwarding; YouTube’s Live Control Room determines how viewers receive the vertical format. If you want both horizontal and vertical viewing, use YouTube’s built-in dual stream or send separate feeds from an encoder.
How the Castr-to-YouTube workflow works
Castr takes a video source and forwards it to the destinations you enable. YouTube controls the vertical layout, preview, and stream-key configuration. Castr’s current live-streaming guide, dated August 4, 2026, describes creating a stream, choosing a hosting region and source, then adding a destination. Its source choices include publishing via RTMP/RTMPS and using a webcam. The exact dashboard labels may change.
For encoder-based workflows, Castr’s multistream guide describes sending a feed to Castr over RTMP or SRT, then adding destinations. That guide is dated May 17, 2023; check your current Castr dashboard for available options and plan-dependent destination limits.
Create a Castr stream and add YouTube
- Create the stream in Castr. In the Castr dashboard, create a live stream and choose a hosting region.
- Choose how to send your source. Select a documented source option, such as Publish via RTMP/RTMPS or webcam. If you use an encoder, configure it to send the feed to Castr using the ingest method offered for your stream.
- Add YouTube as a destination. Choose YouTube in the destination setup. Connect your YouTube account, or enter YouTube’s server and stream key if using the manual connection route.
- Complete the platform fields and enable the destination. Confirm the YouTube destination is toggled on. Castr’s role is to forward the source; enabling the destination does not itself create a separate portrait composition.
Choose how YouTube will produce the vertical format
YouTube documents two ways to stream in both horizontal and vertical formats. Decide which you need before starting: YouTube says a vertical format cannot be added after the stream has begun.
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Option 1: YouTube’s built-in dual stream
YouTube’s Live Control Room can create horizontal 16:9 and vertical 9:16 versions at once. Its default vertical composition is a center crop. You can choose center crop, fit to phone width, or stacked, and adjust zoom and position. This approach adapts the source through YouTube’s layout controls; inspect the vertical preview to ensure the important action, faces, titles, and captions remain in frame.
Option 2: Send separate feeds from an encoder
If your production encoder creates distinct horizontal and portrait feeds, YouTube’s documented workflow uses RTMP(S) and a second stream key for the vertical feed. In YouTube Studio’s Live Control Room, open the Stream tab, select Encoder for the vertical preview, choose RTMP(S), and select the second stream key for the vertical feed. Route each matching format to its corresponding key, then go live from YouTube Studio after configuration.
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When routing through Castr, verify how your encoder’s outputs and Castr destinations map to YouTube’s keys before the event. The available Castr documentation establishes source ingest and destination forwarding; it does not establish that Castr automatically creates or routes a separate portrait composition for every setup.
| Approach | Who creates the portrait composition | What you configure | Trade-off |
|---|---|---|---|
| YouTube built-in dual stream | YouTube’s layout canvas | Choose a vertical layout and check its preview in Live Control Room. | Uses an adapted source with YouTube’s framing controls. |
| Encoder-based dual streaming | Your production encoder | Produce separate matching feeds and route the portrait feed to YouTube’s second vertical stream key over RTMP(S). | Gives the production encoder control over the portrait feed, but requires correct key selection and routing before the stream. |
Preflight: check eligibility, framing, and the feed
- Check channel eligibility. YouTube’s help page says the channel must be verified and must not have had a live-streaming restriction in the previous 90 days. YouTube also states a minimum age of 16 for live streaming.
- Choose your audience formats. Decide whether the production is portrait-only or should serve both horizontal and portrait viewers.
- Check the vertical preview. For YouTube’s built-in dual stream, choose among center crop, fit to phone width, and stacked, then adjust zoom and position as needed. For encoder-based dual streaming, confirm the portrait feed is assigned to the vertical key.
- Confirm the Castr destination. Make sure YouTube is connected and enabled in Castr.
- Test before the event. YouTube recommends preparing encoder streams ahead of time, checking the Live Control Room preview, and monitoring audio and video. Use an unlisted test stream if you want to check the end-to-end result without making the test public.
- If streaming from a mobile device, lock screen rotation, check network speed, and test audio and video with an unlisted stream. YouTube says an external battery pack can be useful, but it is optional.
What viewers see—and what differs by format
YouTube says vertical live streams can be discovered while people browse Shorts and open into a full-screen vertical experience in the YouTube mobile app. This is a possible discovery surface, not a guarantee that a stream will be recommended or seen. The vertical live feed is not currently available on tablets, and scheduled live streams and Premieres do not appear in that feed.
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For YouTube dual streams, horizontal and vertical viewers share a stream URL and chat, but YouTube’s feature table distinguishes some capabilities. It lists vertical-feed discovery, scrollable live streams, and certain fan-funding features for vertical. It lists clickable links in chat or the channel description, live pre-roll and mid-roll ads, 4K broadcast bitrate, Premieres, and Live Redirect for horizontal but not the vertical feed. Feature availability and eligibility can change, so check the current controls in YouTube Studio before relying on a specific feature.
YouTube reports the two streams’ metrics together in Live Control Room during and after the broadcast. Metrics for only the vertical stream become available 24 hours later, according to YouTube’s help documentation.
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Troubleshooting common setup problems
- YouTube does not show a vertical preview: Confirm that the vertical format was configured before going live. For the encoder route, select Encoder in the Stream tab and choose RTMP(S) for the vertical preview.
- The vertical view crops important content: In YouTube’s built-in dual stream layout, inspect the preview and adjust the crop, zoom, or position, or choose fit to phone width or stacked if it better suits the source.
- The portrait feed appears in the wrong format or not at all: Check that the encoder is sending the portrait feed to YouTube’s second vertical stream key and the horizontal feed to its matching key. Confirm the encoder-to-Castr-to-YouTube routing before starting.
- The YouTube destination is not receiving the Castr stream: Recheck the selected YouTube account or manually entered server and stream key, then verify that the destination is enabled in Castr.
- Audio or video is unreliable: Use an unlisted test stream, inspect the Live Control Room preview, monitor both audio and video, and check the network connection—especially for a mobile source.
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