Upload Errors and File Size Limits for Slack Messages
An upload error is frustrating when the message is vague. 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.
Upload Errors and File Size Limits
Most errors come from three causes: the file is too big, the dimensions are outside the allowed range, or the format is not accepted.
For Slack messages, convert to JPEG, resize to about 1600 pixels and compress below 500 KB. If the form lists its own limits, use those numbers instead.
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
- Write a size limit slightly below the stated maximum to leave a margin.
- Process private images locally rather than uploading them to unknown servers.
- Crop out distractions so pixels go to the subject.
- Use WebP where it is supported and you control the page.
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
- Quick Guide: Compress JPEG for Slack Messages in 30 Seconds
Short on time? Here is the fastest route.
- How to Compress JPEG for Slack Messages
Getting a JPEG ready for Slack messages is mostly about two numbers: pixel width and file size.
- Best Image Size for Slack Messages
There is no single magic number, but there is a sensible range for Slack messages.
- Best JPEG Quality Setting for Slack Messages
Quality is the slider people touch first, yet it is often the least understood.
- Quick Guide: Compress JPEG for Landing Pages in 30 Seconds
Short on time? Here is the fastest route.
- Best Image Size for Restaurant Menus Online
There is no single magic number, but there is a sensible range for restaurant menus online.