Slack's documented per-file upload limit is 1GB. Its help page on adding files says it in one unconditional sentence: "You can add files up to 1GB in size."
That number is high enough that most rejected uploads are not actually about it. A 40MB screen recording that refuses to post is not hitting a 1GB ceiling — something else stopped it. The question worth asking is which of four separate mechanisms blocked you, because they have four different fixes.
What Slack's documented limit actually is
One sentence, no conditions attached. The "Add files to Slack" help page states the 1GB figure at the top of the section, and — this matters — that page carries no per-plan table. There is no documented split where Free gets one number and Business+ gets another.
So the widely repeated claim that paid plans raise the per-file ceiling has no official source behind it. To check whether your workspace is an exception, check the official documentation rather than a third-party comparison chart.
Two other details from the same page matter before you troubleshoot:
- Drag and drop is documented for up to 10 files at a time: "Drag and drop up to 10 files into the Slack message field, or click the plus icon next to the message field and choose files to add."
- Slack's documentation does not state a duration limit for uploaded video files. The five-minute figure people remember belongs to clips (see the FAQ), not to uploads.
The fastest fix: make the file smaller before Slack sees it
If the file genuinely is large — a long screen recording, a 4K phone video, a meeting capture — compressing it first is the fix that works regardless of which mechanism rejected it. A smaller file clears the 1GB ceiling, clears an admin-tightened ceiling, and stops eating workspace storage, all in one pass.
Try it right here
Runs in your browser. Your file is not uploaded anywhere.
This runs inside your browser tab. The video is read from disk, re-encoded locally, and handed back — nothing is uploaded to a server, so you are not solving one upload problem by creating another. The "small" preset targets exactly this case: a clip that will be watched in a message pane, not on a television.
For which settings actually move the needle, how to compress a video without losing quality covers the trade-offs. If the file came off a Mac or iPhone as a QuickTime file, MOV to MP4 re-wraps it on the way.
Four reasons an upload gets blocked
Work down the list — the symptoms differ enough to tell them apart.
1. The file is over the documented 1GB ceiling
Symptom: the file is over 1GB. Cause: the documented per-file limit, "up to 1GB in size." Fix: compress or trim. For video this is almost always easy, because bitrate is usually far higher than a chat-window playback needs.
2. Your workspace has been restricted below that
Symptom: the file is nowhere near 1GB, but Slack still refuses it — and a colleague on a different workspace can post the same file fine.
Cause: Slack's developer documentation lists an error for exactly this. In the error table for files.getUploadURLExternal, the code file_upload_size_restricted is described as: "The size of provided file is too large, as the team has restricted uploads of large files."
That is a distinct condition from the 1GB ceiling. It means the size that applies to you is whatever your workspace has been set to, which can be smaller. Slack's developer documentation gives the error text but does not document where that setting lives or what values it accepts, so the practical route is asking a workspace owner or admin what has been configured.
Fix: compress below whatever the local ceiling turns out to be, or ask an admin.
3. The malware scan blocked it
Symptom: the file is small, the workspace is unrestricted, and it still will not go up.
Cause: Slack scans uploads. The note on the "Add files" page is explicit: "Files you add to Slack will be scanned for viruses and other malware, and won't be uploaded if any are detected. If we incorrectly block a file upload, contact us and we can help."
Note the second sentence: Slack acknowledges the scan can be wrong, and points you at support rather than at a workaround.
Fix: scan the file locally. If you are confident it is clean, contact Slack as the page suggests.
4. It is a Slack Connect conversation, and the extension is on the restricted list
Symptom: the file posts fine in your own channels but fails in a shared channel or DM with an external organization.
Cause: Slack Connect has its own file rules. The top of the "Add files" page warns: "Uploading and sharing files may be restricted for Slack Connect conversations, and certain file types can't be added at all. If you can't add files to these conversations, find an owner or admin and ask for help." Slack's dedicated page puts the reason plainly: "To help keep Slack secure, certain types of files cannot be added to Slack Connect channels and direct messages (DMs)."
Here is the part that catches people out. The restricted list for Slack Connect includes archive formats — .7z, .gz and .tar are all on it — while common video containers such as .mp4, .mov, .mkv and .webm are not.
So the instinctive fix makes things worse. Zipping a big video into a .tar or .7z to "make it easier to send" turns a file type that was allowed into one that is blocked outright in Slack Connect. Send the video itself, compressed.
Fix: post the original media file rather than an archive, and if a specific extension is refused, check the current restricted-file-types list in Slack's official documentation before assuming it is a size problem.
One important limit on this rule: it applies to Slack Connect channels and DMs. It is not a workspace-wide ban list, and treating it as one will send you chasing the wrong cause in your own internal channels.
A fifth thing, on free workspaces
Slack's developer documentation also lists storage_limit_reached, described as: "File storage limit has been reached. This occurs when free teams have uploaded 5GB of files."
Read that carefully before repeating it. It is a workspace-wide storage total, not a per-file limit — the per-file figure is still 1GB. And the source is the developer documentation's error table, not a current user-facing help page; Slack's help centre today frames free-plan limits in terms of history, not capacity. Treat it as an error your workspace can return, not as a published storage allowance.
The thing that looks like a failure but isn't
If your file went up and simply does not display, nothing is broken. Slack documents preview behaviour separately from upload behaviour:
"Slack will include a preview of a file as part of your message. If you share an image, the preview will only display inline if it's smaller than 25,000 pixels on the longest side, and less than 45 million pixels total. Microsoft Office files that are larger than 50 MB will not display a preview."
Two things to take from that. First, the two image conditions are joined by and — an image has to satisfy both to render inline, and failing either one is enough to drop the preview. Second, none of these numbers is an upload limit. A 60MB spreadsheet uploads; it just will not show a preview. Slack's documentation gives no equivalent preview threshold for video, so do not apply the image numbers to a video file.
How to tell it worked
Check the file size on disk after compressing, then re-test in the same conversation that rejected it. Testing in a private channel after a Slack Connect rejection proves nothing — those are the two places the rules differ most.
FAQ
What is Slack's file size limit? 1GB per file, per Slack's own help page: "You can add files up to 1GB in size." That page states it without any per-plan breakdown, and Slack's documentation does not publish different per-file ceilings for Free, Pro, Business+ or Enterprise+.
Why does Slack say my file is too large when it is way under 1GB?
Most likely your workspace has been restricted below the documented ceiling. Slack's developer documentation defines file_upload_size_restricted as "The size of provided file is too large, as the team has restricted uploads of large files." Ask an owner or admin what your workspace allows.
Why won't Slack let me upload a zip file?
If it is a Slack Connect channel or DM, archive formats including .7z, .gz and .tar are on Slack's restricted file types list for those conversations. Compressing a video into an archive to shrink it is counterproductive there — send the video file instead.
Does Slack have a video length limit? For clips, yes: Slack describes sharing "audio and video clips up to five minutes long," available on all plans to members and guests. For ordinary file uploads, Slack's documentation does not state a duration limit — only the 1GB size figure.
My file uploaded but there's no preview. Is it corrupted? No. Preview and upload are separate. Images display inline only when they are "smaller than 25,000 pixels on the longest side, and less than 45 million pixels total," and Office files over 50 MB do not get a preview at all. The file is still there and still downloadable.
Why did my older files disappear from a free workspace? Two different mechanisms. Slack hides messages and files older than 90 days once the visibility limit is reached, and upgrading restores "the remaining 275 days." Separately, content "more than one year old will be permanently deleted," and "it will not be possible to restore messages and files once deletion occurs." One catch: if a workspace owner chose to delete messages and files after 90 days, Slack says that setting "will automatically delete any that become hidden by the message and file limit" — then upgrading brings nothing back.
Can I save a video someone sent me in Slack to my phone? Slack's help page says desktop downloads work for files generally, but "on your mobile device, you can only download image files." For video, download it on desktop.
Quotes from Slack's help pages on adding files to Slack, usage limits for free workspaces, restricted file types in Slack Connect, recording clips, and from Slack's developer documentation for files.getUploadURLExternal, checked 16 September 2026. Slack revises these pages — verify before relying on a number. Related: Discord file too large, WhatsApp video too large to send, or browse all Clapr tools.
