Prepare a GIF for your platform
Platform limits and recommended compression targets are different. Check the limit shown in your account before uploading.
| Slack | Custom emoji need a small file and a short animation; file size alone is not enough.
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How to use this tool
- Check that the source GIF has no more than 50 frames and a shape suitable for an emoji.
- Add the GIF here. The free 100KB target is already selected.
- Compress and inspect the actual output size, background, and complete loop.
- Download the file and add it through Slack's custom emoji settings if your workspace permits you to do so.
Leave room below Slack's recommended file size
Slack recommends custom emoji files under 128KB. The 100KB preset is a smaller working target, not Slack's own stated limit. Check the actual result because choosing a target does not guarantee that every source will reach it.
A short loop of simple artwork is a better starting point than a full scene. At emoji size, small captions and background detail may become unreadable even when the file uploads successfully.
Frame count needs a separate check
Slack allows up to 50 frames in a GIF emoji. A file can be small enough in bytes and still exceed that count. CompressGIF preserves the source frames, so it cannot solve a frame-count rejection through file compression alone.
If there are too many frames, shorten or re-export the animation in an editor before returning here. Review the edited loop for a natural transition; a smaller frame count is not useful if the reaction becomes difficult to recognize.
Prepare the picture for a small square
Slack recommends a square image and a transparent background. Choose a subject that remains clear in a small space. Remove unnecessary borders or empty space in an editor when they make the subject appear too small.
This compressor does not automatically crop to a square or remove a background. If it offers a smaller-width retry after missing the target, that resizes the picture; it does not make a rectangular source square.
Separate file problems from workspace restrictions
If the add-emoji control is unavailable, check your workspace permissions rather than repeatedly compressing the file. If Slack rejects the upload, use its error to distinguish file size, animation requirements, and access restrictions.
Free compression supports up to three GIFs per batch, each up to 10MB. GIF contents are processed in your browser without needing to upload those contents to CompressGIF.
Frequently asked questions
Will a GIF below 100KB always work as Slack emoji?
No. It must also meet Slack's animation requirements, and your workspace must allow you to add custom emoji. Check frame count separately.
Does CompressGIF reduce the number of frames?
No. It preserves frames and timing. Use an editor to shorten or re-export a GIF that exceeds Slack's 50-frame limit.
Will the tool make my background transparent?
No. Background removal is not part of compression. Prepare transparency in the source GIF, then inspect its edges after compressing.
Is this also the limit for a GIF in a Slack message?
This page addresses custom emoji. A file attached to a message follows a separate upload flow; do not apply the custom emoji guidance to every Slack attachment.