Shorts spec sheet against Sume Timeline output: what is confirmed

What we can confirm, and what we cannot

You can render a clip for YouTube Shorts with Sume Timeline 1.0 at its default output of 1080 by 1920, up to 180 seconds if you want, and the numbers on the YouTube side come from YouTube's own help page. YouTube's page, read 2026-10-06, says Shorts can be up to three minutes, that the maximum resolution is 1080p, and that the title is at most 100 characters. That is all we state about YouTube. We tried to read Instagram's and TikTok's own spec pages for Reels and for longer TikTok videos and got only navigation text, so this post makes no claim about their aspect ratio, length or file size. Check those pages directly before you publish there.

File size and caption safe zones are the other two questions people ask about specs. Sume's docs print no maximum file size for a Timeline render, so we cannot give one. For captions, the video captions API gives you a placement control, anchor_ratio, the center of the caption line as a fraction of the frame height, which you set to keep text clear of platform interface elements you have checked yourself.

The side-by-side

Left column facts for YouTube come from the cited help page. Right column facts come from the Sume Timeline 1.0 and video captions docs.

An offline pre-flight

The function below checks the parts of the table we can state: even output size inside Timeline's range, a vertical frame, the 180-second ceiling and the 100-character title. It reads a body before you send it and runs without a network. It will not tell you whether YouTube accepts the file, which only YouTube can say.

YOUTUBE_SHORTS_MAX_SECONDS = 180      # YouTube Help, read 2026-10-06
YOUTUBE_TITLE_MAX_CHARS = 100          # YouTube Help, read 2026-10-06

def check_episode(body, title):
    """Offline pre-flight for a Timeline 1.0 body that will become a YouTube Short."""
    problems = []
    out = body.get("output", {})
    w, h = out.get("width", 1080), out.get("height", 1920)
    if w % 2 or h % 2 or not (256 <= w <= 2160 and 256 <= h <= 2160):
        problems.append("Timeline needs even width/height between 256 and 2160")
    if h <= w:
        problems.append("not vertical: a Short should be taller than wide")
    if body["audio"]["duration_seconds"] > YOUTUBE_SHORTS_MAX_SECONDS:
        problems.append("longer than the 3 minutes YouTube lists for Shorts")
    if len(title) > YOUTUBE_TITLE_MAX_CHARS:
        problems.append(f"title is {len(title)} chars, limit {YOUTUBE_TITLE_MAX_CHARS}")
    return problems

ok = {"audio": {"duration_seconds": 58, "mode": "silence"}}
bad = {"audio": {"duration_seconds": 200, "mode": "silence"},
       "output": {"width": 1921, "height": 1080}}
print(check_episode(ok, "Episode 4"))
print(check_episode(bad, "x" * 101))

Using the plan as the second gate

After the offline check, post the same body to POST /v1/timeline-1.0/plan. The plan is unbilled and returns duration_seconds, segment_count, billable_minutes and the estimated cost, so you see the real duration the render would have. Compare it to 180. A plan cannot predict a pad or a loop warning, so keep a gate on the completed render's warnings as well.

If you plan to caption the episode, remember that the standalone captions price is quoted for videos up to 60 seconds. A 3-minute episode is allowed by YouTube and by Timeline, and the caption quote does not cover it, so read the catalog before you commit a season.

Keeping the sheet current

Platform specs change. The October roundup describes a Shorts series feature rolling out from 23 September, and a platform that changes its upload surface this often can change a length or size limit without announcement. Date every row of your own spec sheet, link the page it came from, and re-read it before each batch. The one row we had to leave blank for Instagram and TikTok is the honest state of what we could read, and a blank you notice is better than a number you trust by accident.

If you render for more than one platform, keep one Timeline body per platform even when the numbers match today. A body is cheap, a plan is free, and separate bodies let one platform's rule change without touching the other's. Name them by platform and by version so the ledger shows which spec each file was made against.