Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsIf OBS fails to start a YouTube broadcast, first identify where the failure appears, then refresh the YouTube stream key and update OBS if you use a stream-key connection. YouTube recommends this for third-party encoder startup errors generally, but its cited help guidance does not define a specific OBS–YouTube error numbered 400. The number alone is not enough to diagnose the cause.
First, identify where the error appears
Note the complete error wording and when it appears. “400” by itself does not establish whether the problem is OBS authentication, the connection to YouTube, or the stream after it reaches YouTube.
- During OBS sign-in: You may be using OBS’s account-integration mode rather than a manually entered stream key. That points to an authentication or integration issue.
- When you click Start Streaming: If OBS is configured with a stream key, check the key and connection settings first.
- After YouTube shows a preview or stream-health message: The encoder may already be sending video. Use the specific Live Control Room message to investigate format, bitrate, or another reported problem.
An OBS forum report about an “Error 400” concerned Restream authentication, not a YouTube broadcast-start failure, so it does not establish the cause of this issue.
Refresh the YouTube stream key
YouTube’s documented first remedy for third-party encoder startup errors is to get a new stream key in Live Control Room and update the encoder. Follow this sequence:
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- In YouTube Studio, open Go Live and select the Stream tab.
- Copy the stream key currently shown for the intended stream.
- In OBS, open Settings > Stream, choose the intended YouTube service or connection, and paste the key into the stream-key field. The exact labels can vary by OBS version and connection method.
- Save the settings and try Start Streaming again. Check YouTube’s Live Control Room for a preview or a more specific stream-health message.
If you reset the key in YouTube Studio, replace the old value in OBS with the newly generated one. Resetting requires channel owner or manager permissions. See YouTube’s instructions for managing live stream settings.
Check the encoder connection details
Confirm that OBS is targeting the right YouTube service or server URL and that its key belongs to the intended stream. A valid key for another event or setup may still be the wrong credential for the broadcast you are trying to start.
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YouTube’s encoder workflow uses a server URL and stream key. Start the encoder, then check the Live Control Room preview where appropriate. Follow YouTube’s encoder setup instructions for the workflow you are using.
Separate a local OBS problem from a connection problem
Update OBS to a current version, then inspect the output before changing several settings at once. YouTube recommends using the latest encoder software and checking the local stream and computer when troubleshooting encoder startup.
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- Confirm that your game or other video source appears in the OBS preview and that audio meters respond as expected.
- Look for OBS encoder errors and unusually high CPU load.
- If you have a local recording, play it back to check whether its video and audio are healthy.
- If the local output looks healthy, test the outbound internet connection. A sound local recording does not prove that OBS can reach YouTube reliably.
These checks help distinguish a source or encoding problem from an outbound connection problem; they do not, on their own, prove what caused the 400 response.
Use YouTube’s stream-health message to choose the next fix
When YouTube receives a feed, Live Control Room can show stream errors and health warnings. YouTube distinguishes critical red errors from moderate yellow errors and documents, among other cases, format and bitrate problems. Respond to the message shown for your stream instead of treating every startup failure as a key problem. See YouTube’s live streaming error messages.
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Check OBS encoder settings and test before the event
YouTube’s encoder guidance lists RTMP or RTMPS, H.264, and CBR among its recommended settings. Use settings suited to your selected YouTube workflow and OBS version; the error number alone does not tell you which setting to change. YouTube also recommends testing before the event and monitoring stream health. Consult its current encoder settings, bitrates, and resolutions guidance rather than guessing a bitrate or resolution.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.If OBS signs in to YouTube without a stream key
Some streaming software connects through account sign-in instead of a manually supplied key. If that is how OBS is configured and the error occurs during YouTube login or authorization, refreshing a key may not address it. YouTube says the software provider may need to update its YouTube integration; contact OBS support for help with that connection mode. YouTube’s general live-stream troubleshooting guidance describes the distinction.
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Common causes and practical checks
- OBS has an old or incorrect key: Copy the current key from the intended stream in YouTube Studio and update OBS.
- The key was reset but OBS was not updated: Paste the newly generated key into OBS; do not keep retrying with the prior value.
- The wrong stream or server is selected: Verify the YouTube service or server URL and confirm the key belongs to the intended event.
- The error occurs during account authorization: Determine whether OBS is using sign-in rather than a key; the integration may require support from OBS.
- YouTube reports a format or bitrate issue: Use the exact Live Control Room message and YouTube’s encoder guidance to adjust settings.
- OBS output looks healthy locally but YouTube does not receive it reliably: Test the outbound connection and review OBS’s connection or encoder errors.
Or let it run in the cloud
If your goal is to keep uploaded videos playing as a 24/7 YouTube stream rather than broadcast a live OBS scene, StreamNeo is a cloud option: upload a recording or build a playlist, add your YouTube stream key, and go live. Nothing has to stay on at home. It streams the upload as made, up to 4K 60fps, at one price per slot, and can automatically recover if YouTube drops the stream. The first day is free with no card. Monthly pricing is $9.99 per month. Start your free day with StreamNeo.
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