Substack free portion of a video: cut the public teaser clip

A creator who sells video on Substack can show a free portion inside Substack and publish a separate public teaser clip elsewhere, cut with Sume's video trim at $0.02 a job. The teaser is a file you post to social; Sume does not set Substack's paywall and has no connection to it.

The paywall fact comes from Substack's November 2023 announcement of its video features (read 2026-10-02), which describes a flexible paywall that lets publishers choose a portion of an episode to make free to anyone. The page gives no technical limits, so this post makes none up.

What does Substack's page say about the free portion?

The announcement lists a video-podcast uploader that splits the audio from the video and sends it to a podcast feed, a paywall where you select a portion of an episode to make free, a redesigned video page with a large player, and a clipping tool for extracting timeline segments to share on social media.

Substack therefore already has a clip tool. A separate trim is useful when you want an exact cut length, a specific output size, or burned-in captions in a style Substack's tool does not offer, and when the same teaser is going to places Substack does not post to.

How do I cut a teaser that matches the free portion?

Decide the seconds in Substack first, then cut the same range so viewers see what the free portion shows. Video trim needs the source in your Sume workspace (POST /v1/media-imports), a start, and one of end or duration, plus an Idempotency-Key. Outputs are limited to 900 seconds and sources to 1800.

This cuts the first 90 seconds, frame-accurately:

curl -X POST https://api.sume.com/v1/video-trim \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: episode-12-free-portion" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/episode-12.mp4",
    "start": 0,
    "duration": 90,
    "audio": "keep"
  }'

Should the teaser end on the paywall?

Whether the teaser stops where the free portion stops is a marketing choice. A cut that ends mid-sentence reads as a broken file, so look for the end of a thought. Use video inspect with transcribe: true and segmentation.mode: "sentence" ($0.01 per audio minute) to find sentence ends near your intended cut, then set end to one of them.

Add burned-in captions with video captions, $0.20 for clips up to 60 seconds under the current fixed estimate, because many feeds autoplay muted. A teaser over 60 seconds falls outside the stated price, so check GET /v1/catalog first.

What does this not cover?

For per-episode clip habits, read Spotify clips, 60 to 90 seconds, and for upload specs on the Substack side, Substack video post upload. Track jobs with Jobs and results.

• Setting the free portion: that happens in Substack.
• Upload limits and formats on Substack: see its Help Center, or our guide on Substack video uploads.
• Posting the teaser: Sume returns a file URL, nothing more.
• Rights to music or guests in the footage.

What about vertical teasers?

If the teaser goes to a vertical feed, set output on the trim to a 9:16 size such as 1080 by 1920 and precision to exact, the only precision that accepts an output conform. The docs do not describe how a landscape source is fitted to a vertical frame, so pull a still with video frames and look before you post.

Keep the public teaser distinct from the paid material. The goal is a taste, not a copy of the paid content in a different place.

Name each file after the episode and cut length, for example episode-12-free-90s, so you can tell later which teaser matches which free portion.