How do I cut a 15-second series trailer from my Shorts episodes?

Trim five 3-second beats from your episode masters at $0.02 each, then join them in one Timeline 1.0 render. That is $0.10 in trims plus the render.

YouTube's Help page on Shorts series describes a series as a Shorts-only playlist with seasons and episodes, with each episode at most 180 seconds (read 2026-10-07). A trailer gives viewers the whole season in one clip.

The trim request

POST /v1/video-trim takes video_url, start (seconds, 0 or more) and exactly one of end or duration, and returns a new MP4 of the range [start, end). Idempotency-Key is required. The default mode is async; mode: "sync" waits up to 30 seconds for a finished job.

Optional fields are precision, audio and output. Trims do not change the source file.

Assembly

The trim API does not assemble clips; Timeline 1.0 handles the sequence, transitions and audio. Use the theme from the audio spine post as the single track under the five beats.

The sources have to be Sume-hosted; see the import post for where files come from. Read the Video trim page for the precision options.

• Pick the cliffhangers, not the openings.
• Keep every beat under 4 seconds.
• Render once and reuse the trailer in the playlist description.

Timing a trailer to a season

Release the trailer before episode one, not after episode ten. It sells the series and gives the viewer a reason to follow. Choose beats from across the season, but avoid anything that spoils the last episode.

Trims are exact when you ask for them. precision is an optional field, so check the Video trim page for the values you can send. For a trailer built from short beats, an exact cut is worth it because a few frames of the wrong shot show up immediately.

Keep the five cut points in a table next to the episode masters. When you plan season two, you will want to reuse the same beat order for the new trailer.

Three trailer styles

A countdown trailer shows five beats, each with a number. A mystery trailer shows only reactions. A recap trailer shows the cliffhangers of the last three episodes. All three are built from the same five trims at $0.02, so you can test them for under a dollar.

Pick one style per season, and keep it. Viewers learn to recognize it.

Finally, keep the trailer vertical. Trims keep the source framing, so a trailer cut from 9:16 episodes stays 9:16, which suits the same feed that carries the episodes. Test it by watching it muted on a phone: if the story still reads, add the theme, and if it does not, change the beats.