Image tool / 44
Slack Emoji Maker
Make a Slack custom emoji from any picture: a square 128 × 128 PNG or JPG under Slack's 128 KB limit, previewed on light and dark themes.
Slack Emoji Maker: TOEA draws your picture into a 128 × 128 square in the browser, encodes it as PNG or JPG, and checks it against Slack's 128 KB limit, cutting the palette or the JPG quality automatically when the file would be too large. Runs 100% locally in your browser with zero server file uploads.
- Category
- Image tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
PNG, JPG, WebP, GIF, or SVG · a transparent PNG gives the cleanest result
Background in the way? Cut it out first with Remove background, then bring the transparent PNG back here.
- A square image; 128 × 128 pixels is the recommended size.
- PNG, JPG, or GIF, under 128 KB.
- Transparent PNG looks right in both light and dark themes.
What Slack accepts
Slack takes a square image in PNG, JPG, or GIF, under 128 KB, and recommends 128 × 128 pixels. A non-square picture is fitted to a square by Slack in ways you cannot adjust, so framing it here first keeps control of the crop. Workspace admins can limit who may add emoji; if the option is missing from the emoji menu, that is the reason.
The name becomes the :shortcode: people type, so short and memorable beats descriptive: :shipit: gets used every day, while :q3-launch-celebration-final: does not. Lowercase letters, numbers, hyphens, and underscores are the safe set, and the name field here keeps the downloaded file to those characters.
Light and dark themes
Slack users choose their own theme, and a white square behind a logo looks like a sticker on a dark sidebar. Keep the background transparent, and check the dark preview here. For a company logo, a small margin stops the mark touching the edges of the reaction bubble, and an outline helps a dark logo on a dark theme.
A logo that should also work as a rounded avatar or channel icon needs a second version rather than a compromise between the two. The rounded corner tool makes that version from the same artwork, with transparent corners that sit cleanly on either theme.
How to use it
- Choose an image; logos and faces work best cropped tight.
- Fit or fill the square, adjust zoom and position, and add a margin or outline if it needs one.
- Download the file and add it in Slack under Customize workspace › Emoji.
Privacy & limitations
The picture is processed locally and never uploaded to TOEA or to Slack; you add the file to your workspace yourself.
Related tools
Frequently asked questions
What are Slack's custom emoji requirements?
A square image under 128 KB, in PNG, JPG, or GIF. Slack recommends 128 × 128 pixels and scales larger images down. Your workspace may restrict who can add emoji; if the option is missing, ask an admin.
What should I name the emoji?
Slack usually pre-fills the name from the file name, and you can change it when uploading. Emoji names stick to lowercase letters, numbers, hyphens, and underscores, so the name field here keeps to those.
Why does my emoji look wrong in dark mode?
A white or black background baked into the image shows as a box on the opposite theme. Keep the background transparent, or cut it out with the remove background tool first, and check both previews here.
Can I make a GIF emoji?
Not with this tool: GIFs are read as their first frame and saved as a still.
Free tool · runs in your browser · no account required