Slack
How to make a GIF small enough for a Slack emoji (128 KB)
Slack's custom emoji limit is 128 KB, half of Discord's. Getting an animated GIF under it is very doable, but you have to cut in the right order.
The Slack emoji limit
Slack custom emoji have a 128 KB file cap. Slack displays them tiny (smaller than a line of text), so 128×128 px is the practical size. Anything bigger is downscaled anyway.
Normal GIFs you post in a message aren't affected. Slack's file upload limit is huge. The 128 KB cap is only for custom emoji.
Why most GIFs are way over
A GIF stores every frame as a full image. A two-second reaction GIF at 25 fps is 50 images. At 480×270 px, that's about 6.5 million pixels to store, and even with GIF's compression you're looking at a few megabytes. To get to 128 KB, you need to shrink it by 95% or more.
Step by step
- Crop square. Emoji slots are square. Crop to the face or the action.
- Resize to 128×128 px. This alone often gets you 80–90% of the way.
- Cut the frame rate to 10–12 fps. At emoji size, nobody can tell.
- Shorten it. Emoji loop endlessly, so one clean loop of a second or two beats a long clip.
- Or let Gifpresso do steps 2–4. The Slack emoji preset fits the GIF inside 128×128 px, aims for 120 KB, and trades off frame rate and colours until it fits.
Uploading it to Slack
In Slack, open the emoji picker, choose Add Emoji, upload the file and give it a name. If your workspace restricts who can add emoji, you'll need an admin to do it or to change the setting.
FAQ
Can Slack emoji be animated?
Yes. Upload a GIF and it plays as an animated emoji, as long as it's under 128 KB.
Why is my GIF still over 128 KB at 128×128?
Usually too many frames or a busy, noisy background. Cut the frame rate further or shorten the loop. Flat colours compress much better than photographic footage.
Does Slack accept PNG emoji?
Yes. If it doesn't need to move, a static PNG will be tiny and look sharper than a GIF.