Optimize Images & Videos for Slack - Size Guide 2026
Share files and media efficiently within your Slack workspace.
Slack Image Sizes
| Type | Dimensions | Aspect Ratio | Max Size | Format |
|---|---|---|---|---|
| Shared Image | Up to 4096 x 4096 (preview) | Any | 1 GB per file | JPG, PNG, GIF, BMP, WebP |
| Profile Photo | 512 x 512 | 1:1 | 1 MB | JPG, PNG, GIF |
| Workspace Icon | 132 x 132 | 1:1 | 1 MB | JPG, PNG, GIF |
| Custom Emoji | 128 x 128 | 1:1 | 128 KB | JPG, PNG, GIF |
Slack Video Specs
| Type | Resolution | Max Duration | Max File Size | Bitrate | Format |
|---|---|---|---|---|---|
| Shared Video | Any | Limited by file size and plan | 1 GB per file | Variable | MP4, MOV, AVI, MKV |
| Slack Clip (video message) | 720p | 5 minutes | Auto-compressed | Auto | MP4 (auto-converted) |
Recommended Compression Settings for Slack
Image Compression
- Quality Level
- 85-90%
- Best Format
- JPG for photos, PNG for screenshots with text
Video Compression
- Codec
- H.264 for broadest compatibility
- Video Bitrate
- 2-4 Mbps for inline preview
- Audio Bitrate
- 128 kbps AAC
Quick Tips for Slack
Slack generates image previews up to ~4096px. Upload at this resolution for the sharpest inline display.
Free Slack plans have limited total storage (5 GB). Compress images before uploading to conserve workspace storage.
Slack Clips (video messages) are limited to 5 minutes and are auto-compressed. For full quality, upload the video file directly.
Custom emoji must be 128 x 128 and under 128 KB. Square images work best — non-square images are padded.
Use thread replies for sharing multiple images to keep channels clean. Each file counts against workspace storage.
Free Tools to Optimize for Slack
Use our free browser-based tools to resize, compress, and optimize your media for Slack. No uploads, no signups — 100% private.
Free Image Resizer
Resize images to the exact Slack dimensions with one-click presets. Batch process up to 10 images.
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Reduce image file sizes by up to 80% to meet Slack size limits without visible quality loss.
Compress NowVideo Compressor
Compress videos for Slack with optimal codec and bitrate settings. Save space without losing quality.
Compress VideoFrequently Asked Questions
What is the Slack file size limit?
Individual files can be up to 1 GB. However, workspace storage is limited by plan: Free plan gets 5 GB total, Pro gets 10 GB per member, and Business+ gets 20 GB per member. Compressed files use less of your quota.
Does Slack compress uploaded images?
Slack generates compressed previews for inline display but preserves the original file for download. The preview may look slightly lower quality, but clicking the image and downloading gives you the original file.
How long can Slack video clips be?
Slack Clips (audio/video messages) can be up to 5 minutes long. For longer videos, upload the file directly as an attachment. The maximum file size is 1 GB per file.
What is the best image format for Slack?
Use PNG for screenshots and images with text — Slack inline preview preserves PNG quality well. Use JPG for photographs to keep file sizes smaller. Keep images under 2 MB for fast preview loading.
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