Slack's 1 GB file limit is not the cap that binds a Sume video clip

Slack's help page says you can add files up to 1 GB. A Sume clip will rarely come close, because the caps that shape it are lower: a trimmed cut is at most 900 seconds, a timeline render at most 1800 seconds, and a source is limited by the per-source download cap. If a video fails to go into a channel, the limit is more likely on the Sume side or in the way you attach it.

The Slack limit is from Add files to Slack, read 2026-10-03. The Sume caps are from video trim and Timeline 1.0.

The limits that apply

The table shows which cap you hit first at each stage of a clip's life.

Why file size is rarely the issue

A 900 second clip is 15 minutes. Whether it reaches 1 GB depends on bitrate, which Sume does not let you set, and on resolution, which you can. Sume's timeline default is a 1080 by 1920 MP4, and trim inherits the source unless you pass output.

For a chat message, a short clip is better than a long one anyway, since viewers in a channel rarely watch long files. Cutting to the useful range with start and duration helps the reader more than any size limit.

If an upload fails

Check the order of events. First, did the Sume job finish? The result is read from GET /v1/jobs/:id/result, and its video_url is a media.sume.com artifact. Second, did you download the file completely before posting it to Slack? Third, is the problem the channel or workspace, not the file size?

Slack's page confirms only the 1 GB figure, so look in your workspace settings for anything stricter.

• Poll the job envelope and wait for result_ready.
• Download the artifact, then upload to Slack.
• Trim to the part viewers need.

A short-clip habit

Trim to 30 seconds or less for channel updates, drop audio when the clip is a silent loop with audio: "drop", and link to a longer version rather than attaching it. That keeps chat history light and puts both limits far out of reach.

Using the limits in planning

Because the Sume caps are lower than Slack's, plan around them: keep trims under 900 seconds, renders under 1800 seconds, and sources small enough to import. If a render is long, ask whether viewers need all of it in a channel.

For a recurring report, a fixed 15 to 30 second clip posted each time is easier to review than a variable length one.

A quick troubleshooting order

If a Sume clip will not go into Slack, check these in order: the job reached result_ready, the downloaded file opens locally, and the file is an MP4 you can play. Only then suspect Slack, and then look at workspace settings rather than the 1 GB figure.