How to add a custom emoji to Slack

Slack lets every workspace upload its own emoji — and once an admin's done it, the rest of the team can react and message with it forever. Here's the two-minute version, plus everything you need to know about file sizes, animations, permissions, and the edge cases nobody documents.

TL;DR:save a 128×128 PNG or GIF under 128 KB, open Slack's emoji picker, click Add Emoji, upload, and name it. Done.

Step-by-step (desktop & web)

1. Step 1

   Find or download the emoji image

   Save a PNG or GIF to your computer. The image must be square (Slack squashes non-square uploads), 128×128 pixels, and under 128 KB. Every sticker on Mojindex is already at the right size.

2. Step 2

   Open Slack's emoji menu

   In any message box, click the smiley face icon on the right side of the input. The emoji picker opens. At the very bottom, click 'Add Emoji'.

3. Step 3

   Upload the file

   In the dialog, click 'Upload Image', select the PNG or GIF you saved, and pick a name. The name must be lowercase, with no spaces — use underscores or hyphens. Hit Save.

4. Step 4

   Use the emoji

   Type :name: in any channel or DM. Slack auto-completes once you type the first few characters. The emoji is now available to everyone in the workspace forever.

File requirements

Slack's emoji constraints are strict:

• Format: PNG, GIF, or JPG. SVG is not supported.
• Dimensions: 128×128 pixels. Smaller uploads still work but look pixelated; larger uploads get squashed.
• File size: under 128 KB. Animated GIFs hit this limit fastest — keep frame count low or use a tool like ezgif.com to compress.
• Aspect ratio: square. Slack does not letterbox or crop intelligently — it stretches.
• Name: lowercase letters, digits, hyphens, and underscores only. No spaces, no special characters.

Animated emoji

Animated GIFs are uploaded the same way as static PNGs. Whether they actually animate depends on a workspace setting: Workspace Settings → Customize → Animation. If it's off, the GIF plays as a single frame. The setting is per-workspace, not per-user — so if you can see other GIF emoji animating, yours will too.

Mobile clients show the first frame as a thumbnail and animate on tap, depending on the OS and Slack app version. Don't expect perfect parity with desktop.

Workspace permissions

By default, any member of a workspace can add emoji. Workspace owners can lock this down so only admins (or specific users) can upload — check Workspace Settings → Permissions → Emoji if the “Add Emoji” button is missing.

Enterprise Grid workspaces sometimes have org-level emoji policies that override per-workspace settings. If you can't add an emoji and you're on Enterprise, ask your org admin.

Troubleshooting

• “That image is too big” — over 128 KB. Compress with TinyPNG (static) or ezgif.com (animated).
• “That name is taken” — pick a different one. You can't shadow built-in emoji or another custom emoji's name.
• Emoji is uploading but invisible — likely a transparency issue. Re-export with a transparent background using a real image editor (Figma, Photoshop, GIMP) and try again.
• It works on web but not desktop — close and reopen Slack. The desktop app caches emoji and sometimes lags 30-60 seconds behind.

FAQ

• Can I add an animated GIF as a Slack emoji?

  Yes. Upload a GIF the same way as a PNG. Animations only autoplay if your workspace admin has enabled animation under Workspace Settings → Customize. If animations are off, the GIF still uploads but plays as a static frame.

• What's the maximum file size for a Slack emoji?

  128 KB. Larger files are rejected at upload. If your file is too big, compress it with a tool like TinyPNG (PNG) or ezgif.com (GIF) and try again.

• Why is my emoji blurry or stretched?

  Slack scales every emoji to fit a 22×22 pixel inline display. Upload a 128×128 source — anything smaller pixelates, anything larger gets squashed. Square aspect ratio is required; non-square images get distorted.

• Can I delete or rename a Slack emoji I uploaded?

  Yes. Open Slack → click your workspace name → Customize. Go to the Emoji tab, find the emoji, and use the trash icon to delete or rename. Only the uploader and workspace admins can remove an emoji.

• Does this work on the mobile Slack app?

  Adding new emojis from the mobile app is limited. You can react with existing custom emoji and use them in messages, but uploading new ones requires the desktop or browser app on most plans.