Slack emoji GIF size limits

A Slack custom emoji has to be under 128 KB and no more than 50 frames. Both are small. A GIF pulled off Giphy is usually 1–5 MB, which is ten to forty times over, and Slack will not compress it for you — it just refuses the upload.

What Slack actually asks for

  • Under 128 KB — the one that gets enforced. 128 KB is 131,072 bytes.
  • Up to 50 frames for an animated GIF.
  • Square, ideally transparent— Slack's wording is that square images with transparent backgrounds work best, in JPG, PNG or GIF.

Worth knowing: Slack does not publish a required pixel size. Most guides tell you 128×128, and that is a reasonable target because it is roughly how emoji are displayed — but it is a convention, not a rule. The byte count is the thing that decides whether your upload is accepted.

The 50-frame cap is really a time limit

Fifty frames sounds generous until you divide by the frame rate. At 24 fps that is a two-second clip. At 12 fps it is a little over four seconds. At 8 fps you get six. So the frame cap and the frame rate together decide how long your emoji can be, and you cannot have both smooth motion and length.

For an emoji this is fine — the good ones are a single gesture on a loop, not a scene. Pick the moment first, then set the frame rate to fit it inside fifty frames.

Getting under 128 KB

128 KB is a hard budget, and the levers are the same as for any GIF — just pushed much further than usual:

  • Go small on width. An emoji is displayed tiny, so there is no reason to keep 480 px. Somewhere around 128 px is plenty and cuts the file dramatically, because every frame shrinks at once.
  • Keep it short. One to two seconds. You are capped at 50 frames anyway, and fewer frames means fewer full images stored.
  • Drop the frame rate. 10–12 fps reads fine at emoji size, and halving the rate halves the frame count.
  • Pick a simple clip. Flat colours and a still background compress far better than a busy, moving scene. This matters more at 128 KB than at any normal size.

You can set the width, length and frame rate when you convert your video to a GIF, and watch the size as you go. Everything runs in your browser, so nothing is uploaded. For the caps on other platforms, see the GIF size limits by platform.

Ready to make one?

Convert your video to a GIF →

Questions

What size can a Slack emoji be?
Under 128 KB. Slack's own guidance is that square images under 128 KB with transparent backgrounds work best, in JPG, PNG or GIF. The size cap is the part it enforces strictly.
How many frames can a Slack GIF emoji have?
Up to 50. That is a documented Slack limit, and it is really a limit on length — at 12 fps, 50 frames is about four seconds; at 24 fps it is only two.
Why won't Slack accept my GIF?
Almost always the file size. A GIF from Giphy or a screen recording is usually 1–5 MB, which is ten to forty times over the 128 KB cap. Slack rejects it outright rather than compressing it for you.
What dimensions should a Slack emoji be?
Slack doesn't publish a required pixel size — it asks for square images and scales them down to display. 128×128 is the figure most guides quote and it is a sensible target, but the byte limit is what actually gets enforced.