MUTools

Slack Custom Emoji Generator

Slack Custom Emoji Generator builds 128×128 px, ≤128 KB custom emoji you can upload to Slack as-is. Pick "Text" mode or "Image" mode depending on the source.

Preset phrases

Weight

Horizontal align

Vertical align

Text size

Per line max = honors line breaks, no auto-wrap. Uniform = same size across lines, wraps when needed.

Animation output

Preview

Not generated
128 × 128 (actual size)

How it looks in Slack (22px / 44px × Light / Dark)

—
—
Light
—
—
Dark
File size: — / 128.0 KB

Everything runs entirely in your browser and is never sent to a server.

Slack limits: 128 × 128 px recommended ・ up to 128 KB ・ PNG / GIF / JPG supported.

About Slack Custom Emoji Generator

Slack Custom Emoji Generator builds 128×128 px, ≤128 KB custom emoji you can upload to Slack as-is. Pick "Text" mode or "Image" mode depending on the source.

Text mode includes Japanese and Latin fonts, text/background color, outline, vertical and horizontal alignment, plus three GIF animations — "Blink", "Marquee", and "Zoom". Image mode accepts JPG / PNG / GIF and rescales them to 128×128 (GIF animation is preserved).

All text and images are processed entirely in your browser — nothing is uploaded to a server. Even custom emoji with inside jokes are safe to make. Runs entirely in your browser.

How to use

  1. Choose "Text" or "Image" mode.
  2. In text mode, enter the phrase and tune font, text/background color, outline, and alignment. Preset phrases ("Thanks", "FYI", etc.) are also one click away.
  3. In image mode, pick or drop a JPG / PNG / GIF and adjust cropping and position.
  4. Choose "Blink", "Marquee", or "Zoom" to export as an animated GIF.
  5. Preview, then click "Download" to save a PNG or GIF optimized to 128×128 / ≤128 KB.
  6. Upload it from Slack's "Add custom emoji" screen.

Use cases

  • Operators energizing reactions on a work Slack — turn frequent phrases ("Thanks", "FYI", "On it") into emoji.
  • Adding team member portraits, logos, or mascots as 128×128 Slack emoji.
  • PR teams batch-generating campaign or event emoji for distribution.
  • Community owners adding animated GIF emoji to liven up reactions.
  • Reusing 128×128-ish emoji on Discord and Microsoft Teams, which have similar specs.

Notes

  • Output is automatically tuned to Slack's spec: 128×128 px and ≤128 KB.
  • Image input must be JPG / PNG / GIF and ≤5 MB; anything larger errors.
  • Animated text exports as GIF; static text exports as PNG. Turning off the background gives you a transparent PNG.
  • Slack plays back animated GIFs as reactions, but some clients (e.g., Microsoft Teams) may show only a still frame.
  • Fonts come from a curated set of Google Fonts (Japanese and Latin).

FAQ

Are images uploaded to a server?
No. Generation happens entirely in your browser, so internal assets or personal photos are safe to use here.
Can I make animated emoji?
Yes. Text mode offers Blink, Marquee, and Zoom animations as GIF output. Image mode preserves the original GIF animation while rescaling it to 128×128.
Can the background be transparent?
Turn off "Add background color" in text mode for a transparent PNG. Transparent backgrounds are also supported with GIF animation.
Will this also work for Discord or Microsoft Teams?
Discord targets 256×256 / 256 KB, and Microsoft Teams about 96×96, but the 128×128 ≤128 KB PNG / GIF generated here typically uploads as-is. Check each platform's animated emoji support.
My output is larger than 128 KB.
Encoding automatically targets ≤128 KB. Heavy GIF animations may need quality adjustments — simplify the animation or drop bold styling to recover headroom.