Misskey custom emoji size and the 64KB limit

Last updated: 2026-08-23

Misskey custom emoji are 128×128px and default to 64KB — the strictest cap of any platform here. This covers why the limit is set per server, how to fit inside 64KB, and how to check legibility on both light and dark themes.

Misskey custom emoji specs

Misskey custom emoji are images registered on a server and used as :name: in notes and reactions. Here is what PochiSta exports for Misskey.

Misskey emote specifications
Use / size	Format	Size limit
128×128pxemoji	PNG (static)	64KB
128×128pxemoji	GIF (animated)	64KB

Note: file sizes are shown in KB, where 1KB = 1024 bytes.

Compare every platform in the spec cheat sheet

The size in this table is the default — the 64KB used by misskey.io, the largest instance. Misskey is federated software, and each server's administrator sets its own upload limit, so the number changes depending on where you post.
The official misskey.io guideline states this as 64KiB, which is 65,536 bytes — the same value as the 64KB shown here.

The limit is set per server

On a single service like Discord or Slack there is one limit. Misskey is the same software run by many different operators, so there is no single “Misskey limit”.

If an upload is rejected as too large, check the guidance for the server you are on first
To use the same emoji across several servers, build for the strictest one and save yourself the rework
For text-only stills, staying under 10KB is generally recommended. It keeps both server storage and client loading light

PochiSta compresses to fit the 64KB default automatically. If your server is stricter, the next section lists what to cut, in order of effect.

How to fit inside 64KB

64KB is the strictest cap of any platform supported here — half of Slack's 128KB again. In order of effect:

Reduce the number of colours
Flat artwork such as text with an outline barely changes when quantised, and the colour count drives file size for both PNG and GIF.
Use fewer animation frames
At 64KB there is very little budget per frame. Raising the playback speed keeps the motion readable with fewer frames.
Avoid photos and gradients
A gradient is barely visible at 128px, so there is little to lose. For photos, the monochrome conversion cuts enough detail to fit.
Lower the effect intensity
The wider the shake or spin, the larger the difference between frames and the worse the compression.

Check it on both light and dark

Misskey clients let people choose their own theme, so an emoji that only reads on one of them is a common mistake. White text with a white outline vanishes on a light theme, and black line art sinks into a dark one.

The PochiSta preview switches between light and dark at actual size. Give a bright fill a dark outline (or the other way round) so the silhouette survives either way.

Sources

Custom emoji creation and submission guidelines (misskey.io official help)

Checked against each platform's official documentation on 2026-08-23. Specs change, so check the sources too before you submit.

You can put this article into practice with PochiSta

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