How to make an animated Slack emoji

Animated emojis are just GIFs that respect Slack’s limits: 128 × 128 pixels and 128 KB. Here is how to make one that loads and loops well.

Open the converter

Step by step

  1. Pick a short, simple GIF

    Choose a loop of one or two seconds with a clear subject. Long or busy GIFs rarely fit in 128 KB.

  2. Crop it to a square

    Drop the GIF into the converter and move the square over the part that carries the action.

  3. Generate and check the size

    Click Generate. The tool resizes every frame to 128 × 128 and reduces colours and frames until the file is under 128 KB.

  4. Preview on light and dark backgrounds

    Check the animation on both backgrounds, then download the GIF.

  5. Upload it to Slack

    Add it as a custom emoji and give it a name. See how to add a custom emoji to Slack.

What makes an animated emoji heavy

A GIF stores every frame as an indexed image, so file size grows with the number of frames, the picture area and the number of colours used. At 128 × 128 pixels the area is already small, which leaves frames and colours as the levers.

  • Frames: a 20-frame loop is roughly twice as heavy as a 10-frame loop.
  • Colours: flat illustrations use few colours; photos and gradients use many and dither badly.
  • Motion: when most pixels change on each frame, little can be reused, so the file is large.

How the converter shrinks a GIF

It tries to keep your animation as it is, and only reduces it when needed: first fewer colours, then fewer frames (with delays merged so the loop keeps its duration, up to a maximum of 50 frames), then a slightly smaller size. If it still cannot reach 128 KB, it says so instead of giving you a broken file.

Start from the GIF to Slack emoji converter, or read the full size requirements.

Tips for a smooth loop

  • Make the last frame lead back to the first so the loop does not jump.
  • Crop tight on the action: at 128 pixels, wide shots become unreadable.
  • Use a transparent background if your GIF has one; it looks cleaner on dark themes.
  • If it is still too big, trim the GIF to fewer seconds before converting.

Frequently asked questions

Does Slack allow animated custom emojis?
Yes, animated GIFs are supported as custom emojis, with the same 128 × 128 px and 128 KB limits.
Why does my animated emoji not move in some places?
Slack may show a static frame in some contexts, for example when animations are turned off in preferences. The file itself is animated.

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