Slack GIF Size Limit: 1 GB in Messages, 128 KB for Emoji

The Slack GIF size limit depends on where the GIF goes. A GIF you post in a message or thread is a file, and Slack's help center says you can add files up to 1 GB. It plays inline if it is smaller than 25,000 pixels on its longest side and 45 million pixels in total. A GIF you upload as a custom emoji is the strict case: Slack says square images under 128 KB work best, and a GIF can have up to 50 frames. When Slack says a GIF is too big, it is almost always an emoji upload.

We build Slack Green, which keeps your Slack status green from our servers during the hours you set. We also make the free Slack emoji resizer, which shrinks an animated GIF under 128 KB in your browser and keeps the animation.

Slack GIF limits by where the GIF goes

A GIF above the preview limits still uploads. People see it as a file to click instead of an image playing in the channel. Some workspaces also restrict which files members and guests can upload, especially in Slack Connect channels with other companies.

The steps for each way to post a GIF, from the built-in picker to uploading your own, are in how to add a GIF in Slack.

Slack GIF emoji size limit

Custom emoji are where GIFs get rejected. Slack's help center gives these numbers:

• • File size: under 128 KB works best.
• • Shape: square, ideally with a transparent background.
• • Frames: a GIF can have up to 50 frames.
• • Formats: JPG, PNG or GIF.

A 128 by 128 pixel image is the usual size. Emoji show at 32 pixels or smaller in messages, so a bigger image does not look better; it only adds bytes. Phone screen recordings and GIFs saved from the web are often 2 to 10 MB, which is 20 to 80 times the limit.

The full upload steps, and who is allowed to add emoji, are in how to add custom emoji to Slack.

How to shrink a GIF for Slack

The file size of a GIF comes from four things: pixel size, frame count, number of colors, and how much changes between frames. Cut them in that order:

Crop to a square around the subject.

Scale to 128 by 128 pixels.

Keep 50 frames or fewer. Drop every second frame, or trim the clip to 2 or 3 seconds.

Reduce colors from 256 to 64 or 32. Cartoon GIFs lose almost nothing.

Our Slack emoji resizer does all four in the browser: it resizes every frame, keeps 50 frames spread across the clip if the source has more, and re-encodes until the file is under 128 KB. Nothing is uploaded to a server.

If you prefer the command line, gifsicle does the same:

# Resize to 128x128, cut to 64 colors, lossy compression, optimize
gifsicle --resize 128x128 --colors 64 --lossy=80 -O3 input.gif -o emoji.gif

# Check the result is under 128 KB (131,072 bytes)
ls -l emoji.gif

To make a GIF emoji from a video clip, ffmpeg can take 3 seconds at 10 frames a second, which gives 30 frames:

ffmpeg -t 3 -i clip.mp4 -vf "fps=10,scale=128:128:force_original_aspect_ratio=increase,crop=128:128,split[a][b];[a]palettegen=max_colors=64[p];[b][p]paletteuse" emoji.gif

Slack GIF too big: what the error means

• When adding an emoji. The file is over the emoji limit or has too many frames. Shrink it as above.

• When uploading to a message. The file is over 1 GB, which a GIF almost never is, or your admin blocks that file type in this conversation. Ask a workspace owner or admin.

• The GIF uploads but does not play. It is over the inline preview size, animations are turned off in your Preferences, Accessibility, or the viewer turned them off. A large GIF can also take a while to load on a slow connection.

A GIF that shows as a still image for one person and plays for another is usually that person's accessibility setting, not the file.

Does Slack compress GIFs?

A GIF posted as a file keeps its original file, and people can download it at full size. For emoji, do not count on Slack to shrink an oversized GIF; shrink it first so the upload goes through and the animation stays smooth. The picker GIFs come from GIPHY and load from GIPHY's servers at the size GIPHY serves.

FAQ

What is the max GIF size for Slack? 1 GB for a GIF posted as a file. For a custom emoji, under 128 KB and up to 50 frames.

How many frames can a Slack GIF emoji have? Up to 50, according to Slack's help center.

What size should a Slack emoji GIF be? 128 by 128 pixels and under 128 KB.

How do I make a GIF smaller for Slack? Crop it square, scale it to 128 pixels, cut frames and colors, or drop it into the Slack emoji resizer.

Can I make a Slack GIF emoji bigger in messages? No. Emoji show at a fixed small size. To show a GIF large, post it as a file or use the GIF picker.