Slack Emoji Size Limit & Requirements
A Slack custom emoji must be 128KB or smaller, square, and a JPG, PNG, or GIF. Animated GIFs can include up to 50 frames. Here are the exact limits — straight from Slack — and the fastest way to meet them.
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File size limit: 128KB
Slack rejects any custom emoji over 128KB. This is the hard cap most uploads fail on. A short, low-color GIF compresses under it reliably.
Dimensions: must be square
Slack custom emoji must be square. Slack's help docs specify a square image without an official pixel maximum; 128×128 px is the widely used standard, and Slack scales it down for display. Non-square images are rejected, so crop to a square first.
Frames: up to 50 for animated GIFs
Slack allows animated GIF emoji to include up to 50 frames. A shorter loop also helps the file fit 128KB and keep animating after Slack re-encodes it.
How it works
Know the Slack rules
128KB file size, a square shape, and — for animated GIFs — up to 50 frames. A GIF must meet all three to upload and keep its animation.
Crop, scale, and compress to fit
Use the Slack preset to center-crop to square, scale to 128px, and target 128KB in one step — locally in your browser.
Upload and verify
Download the .gif and add it in Slack as a custom emoji. If it still fails, the file is usually over 128KB or not square.
FAQ
What is the Slack emoji size limit?
Slack custom emoji must be **128KB or smaller**. Files over 128KB are rejected at upload. The limit applies to both static and animated (GIF) emoji.
What dimensions should a Slack emoji be?
A Slack emoji must be **square**. Slack's help center specifies a square image but does not list a pixel maximum; **128×128 px** is the standard size most people use, and Slack scales it down for display. Non-square images are rejected.
How many frames can a Slack emoji GIF have?
A Slack animated GIF emoji can include **up to 50 frames** — this is stated in Slack's own help docs. Staying at or under 50 frames also helps the file fit 128KB and keep animating after Slack re-encodes it.
What file types does Slack accept for emoji?
Slack accepts **JPG, PNG, and GIF** for custom emoji. For animation, use a GIF that fits the 128KB, square, and 50-frame limits.
How do I make a GIF fit the Slack emoji limits?
Use the [GIF compressor for Slack](/slack-emoji-gif) on this site — it crops to square, scales to 128px, and compresses under 128KB locally. See the [step-by-step guide](/how-to-make-slack-emoji-gif) for the full process.
Does this upload my GIF?
No. The compression flow is designed to run locally in your browser.