Compress HEIC Images for Slack
Slack displays images inline in messages and generates previews for shared links. Smaller images load faster in busy channels and improve performance for remote teams. High Efficiency Image Format — the default photo format on iPhones and modern Apple devices. Excellent compression. Use ImageSmith to compress your HEIC images to the ideal file size for Slack — target under 1,000,000KB for optimal performance. Processing is fully browser-based — no server uploads.
Recommended format
JPEG
Max file size
1,000,000KB
Dimensions
800×600 or smaller for inline chat images
✓Slack generates automatic thumbnails — keep shared images under 1MB
✓PNG for screenshots and diagrams, JPEG for photographs
✓GIFs animate automatically in Slack — keep under 10MB for smooth playback
✓Avoid oversized images in channel history — they slow channel loading
Compress HEIC for Other Platforms
Compress HEIC for Slack — FAQ
Slack works best with images under 1,000,000KB. Recommended dimensions: 800×600 or smaller for inline chat images. ImageSmith can compress HEIC images to any target size in seconds.
Slack primarily supports JPEG, PNG, GIF, WEBP. Converting to JPEG is recommended for best compatibility.
Upload your HEIC image to ImageSmith, set a target size under 1,000,000KB, and compress. Slack generates automatic thumbnails — keep shared images under 1MB
Slack supports files up to 1GB on paid plans. However, for smooth inline image loading in channels, keep images under 1MB. Very large images require a click to preview.