How to Compress Images for Slack Messages on Mac
Mac users can compress JPEGs without opening Preview or Photoshop. Shared images live in workspace storage and get re-downloaded by every viewer, so smaller is kinder to everyone.
Recommended settings for Slack messages
| Setting | Starting point |
|---|---|
| Format | JPEG (WebP where accepted) |
| Width | about 1600 px on the long edge |
| Quality | 78 |
| File size | 500 KB or less |
These are practical defaults. If the platform or form you are using publishes its own limits, follow those instead.
How to Compress Images
Drag photos from Finder or the Photos app into the page. Set a maximum width of 1600 pixels and a quality near 78.
Press Compress and download. Because processing happens locally in Safari or Chrome, even large batches are fast and private, which helps when preparing images for Slack messages.
Step by step with TheCompressJPEG
- Open the compress JPEG to 500 KB tool, or the main compressor for custom settings.
- Drop in your image. Nothing is uploaded; it is processed in your browser.
- Set the maximum width to 1600 and the target size to 500 KB.
- Press Compress, check the result and download it.
Quick tips
- Always keep the original file and compress a copy.
- Use JPEG for photos and PNG for logos and line art.
- Name files descriptively with lowercase words and hyphens.
- Check the result on a phone, where most people will see it.
FAQ
What size should an image be for e-learning courses?
A practical default is about 1600 pixels wide and 200 KB or less, unless the destination states its own limits.
Can I compress images for e-learning courses without uploading them?
Yes. TheCompressJPEG runs entirely in your browser, so your images never leave your device.
Is WebP accepted for e-learning courses?
It depends on the platform. JPEG is the safest choice when you are not sure.
Wrapping up
For Slack messages, the reliable recipe is simple: resize to around 1600 pixels, compress at quality 78 or to a 500 KB target, and check the result before you upload. Keep the original so you can always start again.
Related guides
- How to Compress Images for Slack Messages Without Losing Quality
Strictly speaking, JPEG compression always discards something, but you can make the loss invisible.
- Batch Compressing Photos for Slack Messages
When you have dozens of images, consistency matters as much as size.
- Why Your Images Are Too Large for Slack Messages
If an upload keeps failing, the image is usually larger than it needs to be in more ways than one.
- Image File Size Checklist for Slack Messages
Run through this list before you upload.
- How to Compress Images for Landing Pages Without Losing Quality
Strictly speaking, JPEG compression always discards something, but you can make the loss invisible.
- Why Your Images Are Too Large for Restaurant Menus Online
If an upload keeps failing, the image is usually larger than it needs to be in more ways than one.