Slack emoji maker
Any picture,
a Slack emoji.
Crop the part you want, and get a square 128 × 128 PNG under Slack’s 128 KB limit, with its transparent background kept. The page says how many bytes it is and what was traded. Nothing is uploaded.
128 × 128 · under 128 KB · PNG
Drop a picture here
PNG, JPG, WebP or SVG · up to 8192px on the longest side
Choose a picture and frame it; the file is fitted under the limit as you go.
Questions
What size does a Slack emoji have to be?
Slack’s help centre asks for square images under 128 KB, in JPG, PNG or GIF, and says transparent backgrounds work best. It does not state a pixel size; this page writes 128 × 128, which is the size Slack’s emoji are drawn from. The limit is read as 128,000 bytes, the stricter of the two ways “KB” is used, so the file fits under either.
Why PNG and not JPG?
JPG cannot keep a transparent background, and an emoji with a white square behind it looks wrong in dark mode. PNG keeps the transparency, and at 128 × 128 it is well under the limit.