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Compression guide

How to compress video for Slack

Slack's per-file limit is 1 GB across all tiers. The real constraints are workspace storage quota (free: 5 GB total; paid: up to 1 TB/user) and team etiquette. Compress to ~50 MB to be a good teammate even though Slack will accept much larger.

Size limit

1000 MB

Target output: 50 MB (with safety margin)

Free / Pro: 1000 MB

Business+: 1000 MB

Enterprise (configurable): 1000 MB

Recommended settings

CodecH.264
CRF (quality)23
Audio bitrate128 Kbps AAC
QuickVid modeRecommended

ffmpeg one-liner

For terminal-comfortable users, here's the exact command:

ffmpeg -i input.mp4 -c:v libx264 -crf 24 -preset medium -vf scale=-2:720 -c:a aac -b:a 128k -movflags +faststart output.mp4

Install ffmpeg via Homebrew: brew install ffmpeg

Tips

  • •1 GB per file but workspace-wide quota matters — Slack admins see who fills the storage
  • •Slack's preview generation works best on H.264; HEVC sometimes fails to thumbnail
  • •For screen recordings, 720p at CRF 24 hits a good size while keeping text readable
  • •Use Slack Clips for in-Slack video recording (built-in tool); they handle compression automatically

Skip the terminal

QuickVid Compress wraps these settings into a one-click "Recommended" mode. Drop your video, pick the mode, save the result. About 30 seconds end-to-end.

Try QuickVid

Related reading

Frequently asked questions

What is the video size limit for Slack?

Slack's default video size limit is 1000 MB. Free / Pro: 1000 MB; Business+: 1000 MB; Enterprise (configurable): 1000 MB. To fit comfortably below the limit, target 50 MB when compressing.

What's the best codec for Slack?

H.264 at CRF 23 produces the best balance of size and quality for Slack. 128 Kbps AAC audio is the right pairing — universal compatibility and small footprint.

How do I compress a video for Slack on Mac?

Drop the file into a Mac compressor like QuickVid Compress (use the "Recommended" mode) or run the ffmpeg one-liner: ffmpeg -i input.mp4 -c:v libx264 -crf 24 -preset medium -vf scale=-2:720 -c:a aac -b:a 128k -movflags +faststart output.mp4. Both produce output that fits Slack's 1000 MB limit with no visible quality loss.

Why does Slack reject my video?

Most rejections are file-size related: Slack caps at 1000 MB. Other reasons include unsupported codec (use H.264 for maximum compatibility, not HEVC), missing the +faststart flag (which keeps streaming usable on slow connections), or audio in a non-AAC container.

Can I send larger videos via Slack?

Slack offers higher limits on paid tiers — Enterprise (configurable) accepts 1000 MB. Alternatively, host the video elsewhere (YouTube unlisted, Google Drive, Dropbox) and share a link. For sensitive content where you don't want third-party hosting, compress aggressively to fit the free tier.