Slack emoji resizer

Turn any image or GIF into a Slack custom emoji: square, under 128 KB, animated GIFs trimmed to Slack’s 50-frame limit with timing kept.

Drop a GIF, PNG, APNG, JPEG or WebP

Choose a file

Output: 128×128, under 128 KB. Animated or still. Runs on your device; nothing is uploaded.

Edge background (animated GIF output)GIF can’t store soft edges; blending them into your chat background makes outlines smooth there.

Slack custom emoji requirements

Formats	JPG, PNG or GIF
Shape	Square works best
File size	Under 128 KB works best
Animated GIF	Up to 50 frames

From Slack’s help page on custom emoji, checked 2026-10-29.

How it handles long GIFs

If your GIF has more than 50 frames, the resizer keeps evenly spaced frames and stretches each one to cover the frames it replaces, so the animation runs at the same speed. Then it fits the file under 128 KB the same way as our Discord tools: fewer colours, gentler dithering and reusing pixels that didn’t change, scored against your original.

Same emoji for Discord? Use the all-platform emote resizer to get every size at once.

Questions

What size should a Slack emoji be?

Slack recommends square images under 128 KB with a transparent background, in JPG, PNG or GIF. This tool makes 128×128, which stays sharp everywhere Slack shows emoji.

How many frames can an animated Slack emoji have?

Up to 50. Longer GIFs keep every second (or third) frame, with timing adjusted so the animation lasts as long as the original.

Why is my GIF emoji not animating in Slack?

Check the frame count and size. Drop it into the upload checker to see whether it breaks a rule.

Is my image uploaded?

No. Everything runs in your browser.