How to Make Custom Slack Stickers (Size & Format)
Want to add your face as a custom emoji? Slack rejects it? Here are the exact rules to get it approved.
1
Size Limits
Slack emojis must be square and under 128KB. If you upload a 5MB photo, it will fail.
2
Transparency
Always remove the background and save as **PNG**. JPG emojis look unprofessional with white boxes around them.
3
Animation
Slack supports animated GIFs for emojis. Keep the frame count low to stay under the 128KB limit.