Reddit's 15-second view rule: a lip-sync clip that stays under it

A single Sume MiniMax H3 Max lip-sync clip is at most 14.8 seconds of audio, which sits under Reddit's 15-second line for its Engaged Video Views beta. A platform roundup reports that Reddit opened a 15-second Engaged Video Views public beta on 2026-09-01, and that videos longer than 15 seconds bill at 15 (Orthotropy, read 2026-10-06). The source does not describe what counts as an engaged view, so do not build a budget on that metric from this page alone.

What it supports is a narrower design choice: if your ad is a talking presenter, a clip of 5 to 14.8 seconds fits a 15-second unit with no second of overrun, and the Sume route is built for that window.

How does the window line up?

What should the clip contain?

A 15-second unit is short, so put the one thing you want said in the first two seconds. Write a single sentence of around 35 to 40 words at a normal pace, produce the audio with Sume TTS, measure it, and send the measured length as duration_seconds. The API rejects values outside 5 to 14.8 instead of clamping, so a measured 15.2 seconds fails cleanly rather than losing your last word.

Pick the resolution by placement, not habit. Feed placements are viewed small, so 480p or 768p is usually enough; the derived Sume rates are $0.0625 and $0.10 a second, which makes a 12-second clip $0.75 or $1.20. Spend on 1080p only when you have seen the difference in the placement itself.

Input limits to plan around

The Sume H3 Max lip-sync request takes a Sume-hosted audio_url of at most 10 MB, and the 5 to 14.8 second rule applies to that audio. The duration_seconds you send is only the reservation basis, and the price is ceil(duration_seconds) times the per-second rate, which is why a 14.8 second clip is billed as 15 seconds in the table above. The list above for 1080p is $0.20 a second, so a 14.8 second 1080p clip is $3.00 against $1.50 at 768p.

Put another way, the cheapest way to stay inside a 15-second unit is also the way the docs describe: measure the real audio length, send it as duration_seconds, and let the API refuse anything outside the window instead of trimming silently.

What about your own spec check?

Reddit has its own ad specifications, and stored Sume guidance on them lives in the Reddit video ad specs post. Check the file against them before upload; this page does not restate platform requirements it did not read. Sume's lip-sync output is an MP4 on a media.sume.com URL, and the job result reports where it is.

Remember the beta label. Reddit's rule was reported as a public beta from 2026-09-01 and could change. Keep the clip length a variable in your pipeline rather than a constant, so a change on the platform side is a one-line edit. If your concept needs more than 14.8 seconds, split it into two ads with their own hooks rather than one long one, because each part must still be at least 5 seconds. The window post covers where to cut.

What would you test first?

Make three versions of the same single sentence at 8, 12 and 14.8 seconds, with different hooks, and compare how each reads in the placement. Since the platform unit reported is 15 seconds, a shorter clip does not save money on that metric, but it may hold attention better. The test is cheap on Sume: three 768p clips at the documented $0.10 a second cost $0.80, $1.20 and $1.50.

Record the results with the date, and re-test when Reddit changes the beta, since the rule is reported from the beta stage and may not stay as it is.