After a lesson is uploaded to Cloudflare Stream you can set a poster — the image on the course card and in the player before playback starts.

Setting a poster

1. Open your course → Videos.
2. For each lesson choose a poster mode:
   • Frame from video — set time in seconds (thumbnail_time_seconds).
   • Custom cover — upload an image (poster_url is stored in R2).
3. Save. In a revision draft, posters are stored in course_revision_videos and moderated with the course.

Video upload (TUS)

1. Initiate — POST /api/courses/:id/initiate-video-upload/videos (returns uid and upload_url).
2. Upload the file via TUS to upload_url (web or iOS background queue).
3. Complete — POST .../tus-complete-new/videos with the stream_uid from step 1.

If step 3 is not called within 24 hours, the orphan Stream asset may be removed by a daily cron job (see Stream upload troubleshooting).

Tips

• Match the course card aspect ratio (4:5) when possible.
• Preview on a phone — the default Stream frame can look too dark on small screens.