YouTube in-feed ads have no max length, but video-trim caps at 1,800 s

An open-ended platform limit is not an open-ended tool. Google's video specs page lists no maximum length for in-feed video ads, and none for masthead ads either (read 2026-10-07). Sume's video-trim accepts a source of at most 1,800 seconds and returns at most 900, so a 40-minute recording cannot enter it at all.

Know the caps before you promise a long in-feed cut.

Platform side versus Sume side

From Google Ads video ad specs and the Sume docs for video trim, Timeline 1.0, and audio detach.

A guard before you submit

The trim route refuses an out-of-range job, but you can fail faster locally. This function mirrors the documented source and output caps and the 0.2-second minimum, and reports the first problem it finds.

def check_trim(source_s, start, duration):
    if source_s > 1800:
        return "source_duration_exceeded: over 1800 s"
    if duration < 0.2 or duration > 900:
        return "duration must be 0.2-900 s"
    if start < 0 or start >= source_s:
        return "start outside the source"
    return "ok"


for case in ((2400, 0, 600), (1700, 100, 900), (1700, 100, 901)):
    print(case, check_trim(*case))

What to do with a longer source

If the recording is over 1,800 seconds, split it before it reaches Sume, with whatever tool made the recording, and import the parts as separate clips. Then trim each part and join the keepers in Timeline 1.0, whose slots accept 0.2-second minimums and whose output can reach 1,800 seconds.

Remember the import step: every Sume URL must already be a media.sume.com artifact, per Media inputs. No off-host URL is fetched.

Is long better here?

The page gives no recommended length for in-feed, so I will not argue for one. A longer ad also means a larger file; check the probe's size_bytes against whatever your upload step allows.

Practical ceilings in a real workflow

Most ad masters are well under 10 minutes, so the 1,800-second source cap matters only for raw recordings: webinars, live streams, events. For those, the first job is selecting the minute or two that works as an ad, which is an editorial step before any API call.

If you do hit a cap, the error is stable and named, such as source_duration_exceeded, so a script can catch it and tell the operator what to do, rather than retrying a job that can never succeed.