Slack Video Compressor

Compress for Slack's 1GB upload cap, Clips 5-minute limit, and Free workspace 90-day history rules.

Local processing only — your file never leaves the browser

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Drag & drop a video, or tap to select

MP4 / MOV / WebM, up to 500 MB

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Slack upload safe (≤ 950MB): leaves a safety margin under the 1GB cap. Best when you need to push a long or high-quality clip through.

⏱ Slack Clips are limited to 5 minutes. Longer videos must go through a regular file upload or an external link (e.g., Drive). For short updates, trimming may be enough.

Resolution (downscale for long videos — sets height; portrait videos get a narrower width)

⚠ This setting may not hit the target size. Try one of: ① trim the video shorter / ② lower the resolution further / ③ pick a larger preset.

Duration (sec) — fill in only if auto-detect failed

Processing… 0%

Original

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→

Compressed

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Download compressed video

Useful next tools

Popular uses

Videos over Slack 1GB capLightweight sharing for Free workspacesClips 5-minute limit guidance

Next tools

Video Trim Tool Video Compressor File Size Estimator

What this tool does

Slack upload-safe preset (≤ 950MB) with a safety margin under the 1GB cap
Light (≤ 25MB) preset for Free workspaces and quick sharing
Auto bitrate math based on duration to hit the target size
Compatibility-first output: MP4 (H.264 + AAC / yuv420p / faststart)
Clips 5-minute notice appears automatically for longer videos
Documents non-size failures (Slack Connect restrictions, malware scan blocks)

How to use

1
Add a video
Drop a file (up to 500 MB) or pick from your device.
2
Pick a preset
Slack upload safe (≤ 950MB) / Quick share (100MB) / Light (25MB).
3
Adjust resolution if needed
For long videos, downscaling (1080p → 720p / 540p) is the fastest way to reduce size.
4
Compress & download
Download the compressed MP4 and upload directly to Slack.

What each setting means

Preset

Slack upload safe (≤ 950MB) = safe under the 1GB cap. Quick share (≤ 100MB) = lightweight sharing. Light (≤ 25MB) = Free workspace use when you treat Slack as a sharing layer.

Resolution

Original / 1080p / 720p / 540p. Downscaling is the biggest size-reduction lever for long videos.

Audio bitrate

Set per preset (192 / 128 / 96 kbps). Speech-heavy content sounds fine at 96–128 kbps.

Output format

MP4 with H.264 + AAC, yuv420p, and faststart for broad device and Slack compatibility. Useful even when source is HEVC / VP9 / AV1.

Recommended settings

Just need it to upload to Slack

Slack upload safe (≤ 950MB) + Original (or 720p if needed)

Primary goal is staying under 1GB. For long videos, resolution is the biggest lever.

Teammates need to watch quickly in a thread

Quick share (100MB) + 720p + 128 kbps audio

Smaller files load faster and play smoothly on mobile.

Free workspace: share now, don't store long-term

Light (25MB) + 540p–720p + 96 kbps audio

Free workspaces have strong history/retention constraints, so treat Slack as a sharing layer.

Short update via Clips

Trim to ≤ 5 minutes → Quick share or Light

Slack Clips are limited to 5 minutes, and shorter videos get watched more.

Common pitfalls

Symptom: Still can't upload after compression

Cause: The conversation may be a Slack Connect channel/DM with restricted uploads, or workspace settings may block uploads.

Fix: Confirm whether it's Slack Connect and ask an owner/admin to adjust settings if needed.

Symptom: Upload fails even below 1GB

Cause: Slack scans uploads for viruses/malware and may block a file (including false positives).

Fix: Try re-exporting with a different filename; if you suspect a false positive, contact Slack support.

Symptom: Quality looks bad / blocky

Cause: Target size is too small for the duration (video bitrate becomes too low).

Fix: Raise the target size, trim the clip, or downscale resolution.

Symptom: Browser freezes / job fails

Cause: Device performance, memory limits, or very large/long inputs.

Fix: Run on desktop, or trim the video first.

Symptom: Old files aren't visible in Free workspaces

Cause: Free has history/visibility limits and retention policies that can remove older data over time.

Fix: Don't use Slack as storage; keep originals in Drive/Dropbox and share links.

Equivalent FFmpeg commands

Reference commands you can run on the desktop FFmpeg CLI.

Stay under Slack 1GB (5-min video example)

ffmpeg -i input.mp4 -map 0:v:0? -map 0:a:0? -c:v libx264 -preset veryfast -pix_fmt yuv420p -b:v 24000k -maxrate 26400k -bufsize 48000k -c:a aac -b:a 192k -movflags +faststart output.mp4

Bitrate back-calculated from 950MB and a 5-minute duration.

Downscale to 720p targeting 100MB

ffmpeg -i input.mp4 -vf scale=-2:720 -c:v libx264 -preset veryfast -pix_fmt yuv420p -crf 23 -c:a aac -b:a 128k -movflags +faststart output_720p.mp4

Downscaling is the biggest size win for long videos.

Light preset equivalent (smallest)

ffmpeg -i input.mp4 -c:v libx264 -preset veryfast -pix_fmt yuv420p -crf 28 -c:a aac -b:a 96k -movflags +faststart output_light.mp4

Browser support & limits

Browser-only FFmpeg (WASM): 500 MB input cap; trim long videos beforehand.
Output is compatibility-first MP4 (H.264 + AAC). Re-encoding is lossy.
Slack-side restrictions (Slack Connect limits, malware blocks) may still prevent uploads after compression.

Privacy

This tool runs ffmpeg.wasm directly in your browser. Files never leave your device — everything runs locally. Read the privacy policy →

Frequently asked questions

What is Slack's file upload limit?

Slack's help center states you can add files up to 1GB. That article doesn't specify plan-based differences.

Does the Free plan limit files too?

Yes. Free workspaces have strong history/visibility limits, and retention settings can delete older data.

How are Clips different from uploading a video file?

Clips are recorded/shared inside Slack and are limited to 5 minutes. Longer content is better as file uploads or external links.

Why can't I upload even after shrinking the file?

Not all failures are size-related: Slack Connect restrictions, workspace settings, or malware scan blocks can stop uploads.

Why output H.264 + AAC MP4?

It's the safest compatibility baseline across devices and playback contexts.

My 25MB target looks terrible — what now?

Trim duration first, then downscale resolution. Duration is the biggest driver of required bitrate.

Is Slack meant to store files long-term?

Slack states it's not intended to be a file/log storage repository. Use external storage for originals.

Related tools

In depth: context unique to this tool

Slack's three video systems: Files vs Clips vs Huddles

Slack actually has three independent video pipelines, and choosing the right one matters more than picking the right compressor. (1) Regular file attachment (what this tool targets): up to 1 GB, permanent URL, thumbnail preview, searchable. (2) Clips (record inside Slack): max 5 minutes, auto-transcription, scoped to the workspace. (3) Huddles (impromptu voice/video calls): free tier limited to 2 participants for 30 minutes, optional recording.

If your clip is under 5 minutes, Clips is usually the better answer: it stays inside Slack end-to-end and the auto-transcript makes it searchable. If it's an existing file longer than 5 minutes, regular attachment (this tool) is the path. For interactive feedback in real time, Huddles. This tool exists for the 'long existing clip, file attachment' case; keep the Clips alternative in mind for shorter recordings.

How the Free plan's 90-day window changes video workflows

Since September 2022, Slack Free workspaces only show the most recent 90 days of messages and files (replacing the old 10,000-message cap). Video uploaded to a Free workspace effectively disappears from search results after 90 days. The file technically stays in Slack's storage and can be revived by upgrading to Pro / Business+, but while you're on Free the file is unreachable.

This is exactly why the tool offers a 'Light (25 MB)' preset. On Free, Slack isn't a video repository — it's a transient sharing layer. Keep originals in Google Drive / Dropbox and use Slack for link sharing. If you've already compressed a video through this tool and it matters long-term, save the output to external storage too.

Why Slack Connect / External Workspace uploads fail

Slack Connect (shared channels between organizations) runs on a different security policy than internal channels. Cross-org file sharing may be disabled, certain MIME types blocked, or the malware scan may produce false positives. Video files are larger, scans take longer, and timeouts cause silent upload failures. Result: 'My file is under 1 GB but it won't upload.'

Compression alone can't fix Slack Connect policy issues, but smaller files do scan faster and improve success rate. If the 950 MB preset fails, try the 100 MB preset. The deeper fixes: (1) ask the Connect-origin admin to enable file sharing for your org pair, (2) upload to Drive and share the link, (3) switch to a direct DM if you're a member of the other workspace.