Slack File Size Limit: 1 GB Per File, and the Limits That Actually Bite
Slack File Size Limit: 1 GB Per File, and the Limits That Actually Bite
The Slack file size limit is 1 GB per file, and it is the same on every plan — Free, Pro, Business+ and Enterprise Grid all share that ceiling. Paying more does not raise it.
Which is worth knowing mostly because the 1 GB limit is almost never what stops you. Two other constraints do the actual damage, and both are easier to hit and harder to notice.
The Three Limits, in the Order They Will Affect You
1. Workspace storage — the one that actually bites. Every file uploaded counts against a shared pool for the entire workspace. Free workspaces get a fixed, fairly small allowance; paid plans scale with the number of members. Fill it and uploads start failing for everyone, regardless of individual file sizes. Slack's per-plan numbers change often enough that the current Slack plan comparison is the only reliable source.
2. The 90-day window on the free plan. Free workspaces can view and search only the most recent 90 days of messages and files. Older material stops being reachable and is eventually removed. This is not a size limit, but it produces the same outcome — the file is not there when you need it.
3. The 1 GB per-file ceiling. Real, but you have to be sending substantial raw video to reach it.
The failure mode that confuses people: when the workspace pool is full, Slack's error reads like a problem with your file. You compress it, retry, and it still fails, because the file was never the issue. If an upload fails on something well under 1 GB, check workspace storage before you touch the file.
Slack Does Not Compress Your Uploads
This distinguishes Slack from most messaging tools and it cuts both ways.
WhatsApp, Discord and Telegram all re-encode video on upload — a 200 MB clip arrives noticeably softer. Slack does not. It generates preview thumbnails for images and video, but the file a colleague downloads is byte-for-byte what you uploaded.
Good: quality is preserved exactly. Send a client a master file and it arrives as a master file.
Bad: your 800 MB screen recording consumes 800 MB of the workspace pool, permanently. There is no invisible compression quietly saving you. On a team sharing recordings daily, this is what fills the quota.
The practical consequence: compress before uploading, not because Slack requires it, but because nothing else will.
Getting Files Under the Limit
Video is nearly always the problem
Video is the overwhelming majority of oversized Slack uploads, and it is also the most compressible thing you can send.
A 10-minute screen recording at 4K straight out of QuickTime can easily exceed 1 GB. The same recording at 1080p with sensible encoding lands around 100-200 MB with no meaningful loss for something being watched in a Slack preview window.
Three changes, in order of impact:
Drop the resolution. Screen recordings captured on a Retina display are often 2880×1800 or larger. Nobody is watching that in a chat client. 1080p removes the majority of the file size immediately.
Re-encode with a modern codec. H.265 delivers roughly 50% smaller files than H.264 at equal quality. See HEVC vs H.264 for where that tradeoff holds and where it does not.
Trim the dead air. The 40 seconds of finding the right window at the start is pure file size.
If the source is a meeting recording, compressing a Zoom recording covers the specifics, and reduce screen recording file size handles the capture-side settings that stop the problem happening again.
Images add up quietly
A single photo will not trouble a 1 GB limit, but design teams posting full-resolution exports all day consume storage faster than anyone expects. A 12 MB PNG export that would be a 400 KB WebP or AVIF is a 30x difference, repeated dozens of times a week.
For screenshots specifically, PNG is usually the wrong default — worth reading best image format for websites even though the context is different, because the format logic is the same.
PDFs are usually mostly images
An oversized PDF is nearly always a document with uncompressed scans or full-resolution embedded photos. Compressing the embedded images typically cuts the file by 70-90% with no visible change to the text. How to reduce PDF size covers the approach.
When to Stop Compressing and Use a Link
Compression has a floor. If a genuine 4K master needs to reach someone at full quality, compressing it to fit Slack defeats the purpose.
Use cloud storage and share the link when:
- The recipient needs the original quality
- The file is above 1 GB after reasonable compression
- Several people need it over a long period — a link survives the free plan's 90-day window; an upload does not
- The workspace is near its storage ceiling
Slack's Google Drive, Dropbox and OneDrive integrations keep shared links previewable in-channel, so this costs very little in convenience. How to send large video files covers the wider set of options.
Reclaiming Storage That Is Already Gone
If the workspace is full, deleting messages is not the fix. Deleting a message containing a file does not reliably remove the file from storage.
Workspace admins can browse files directly in workspace settings, sort by size, and delete the largest. In most workspaces a handful of old video files account for a surprising share of the total.
Two habits that prevent recurrence:
Compress before uploading, not after. Once a 900 MB file is in Slack it is consuming the quota until someone hunts it down.
Put anything that matters somewhere else. Slack is a conversation tool. On the free plan especially, treating it as a file archive means discovering in 90 days that the archive was temporary.
Compressing Files Before You Upload
Doing this per-file — opening a video editor, exporting at a lower resolution, waiting, checking the size, trying again — is the kind of friction that ends with people uploading the 900 MB original.
Compresto compresses video, images, GIFs and PDFs in batch on macOS. Drag in a folder, set a target size or quality level, and it processes everything at once with hardware acceleration, so a large screen recording takes seconds rather than minutes.
Because it runs entirely locally, nothing is uploaded to a third-party compression service on the way to Slack — which matters when the file is a customer call recording or an unreleased design.
Related: compress GIFs for Slack emoji if the problem is custom emoji rather than file uploads, and email attachment size limits for the equivalent constraints elsewhere.
Frequently Asked Questions
What is the Slack file size limit?
1 GB per file, identical on every plan including Free. What varies by plan is total workspace storage, not the per-file ceiling. Audio and video clips recorded inside Slack are capped separately at 5 minutes.
Why does Slack say my file is too large when it is under 1 GB?
Almost always because workspace storage is full, not because the file is oversized. Slack's error wording obscures this. An admin can check usage in workspace settings; deleting old files frees space, deleting messages generally does not.
Does Slack compress files I upload?
No. It creates preview thumbnails, but the downloadable file is the original, unchanged. A large upload consumes its full size from the workspace quota, which is why compressing beforehand matters more on Slack than on platforms that re-encode for you.
Do files deleted from Slack free up storage?
Only when the file itself is deleted. Removing a message that contained a file does not always remove the file. Use the files browser in workspace settings to find and delete large files directly.
What happens to Slack files after 90 days on the free plan?
Free workspaces can view and search only the last 90 days. Older files become inaccessible and are eventually removed permanently. Anything worth keeping belongs in cloud storage, not Slack.
How do I send a file larger than 1 GB on Slack?
Compress it below the ceiling — realistic for most video and PDFs — or upload to Google Drive, Dropbox or OneDrive and share the link. Slack's integrations keep those links previewable in-channel.
What is the best way to compress a video for Slack?
Drop the resolution to 1080p first, since that removes the most size for the least visible loss, then re-encode with H.265 and trim unused footage. For a typical screen recording that combination reliably turns a multi-gigabyte file into something under 200 MB.