How to Make an Emoji Background Transparent for Slack

To make an emoji background transparent for Slack, remove the background from the image and save it as a PNG or GIF. A JPG cannot store transparency, so it always keeps a solid background that shows as a white or colored box, most visibly in dark mode. The fastest free way is our Slack emoji maker: drop in the image, tick Remove background, and download a 128 by 128 PNG. On a Mac, Finder's Remove Background quick action works too, and on Windows 11 so does the Remove background button in Paint.

Slack's help center says square images under 128 KB with transparent backgrounds work best for custom emoji. The steps for each device are below.

Our emoji maker and Slack emoji resizer run in your browser, and the image never leaves your device.

Why a transparent background matters in Slack

On 31 October 2026 we uploaded the same green check twice to our test workspace with Slack's emoji.add method: once as a PNG with a transparent background, once saved as a JPG, which filled the background with white. Slack accepted both and kept the JPG as a .jpg file. Then we used both in a message and as reactions. With the pointer over the message, Slack greys the row, and the JPG shows its white square both in the text and inside its reaction pill:

On a plain white message, the JPG looks fine, because the white blends into the white message area. Hover over the message, react with it, switch to dark mode, or look at it in a message someone has highlighted, and the white square appears. Many of your coworkers use dark mode, so a background you cannot see on your screen is plain on theirs. A transparent emoji drawn only in thin black lines has the opposite problem; our Slack dark mode test shows both cases side by side.

A transparent background also lets the emoji sit cleanly on a status, in a reaction pill, and next to other emoji.

Ways to remove an emoji background

In the browser with the slack.green emoji maker

• Open the Slack emoji maker and choose Image to emoji.
• Drop, choose or paste your PNG, JPG, GIF or WebP.
• Crop it to a square with the zoom and position sliders.
• Tick Remove background. It clears the color around the edges. Move the Tolerance slider up if some background is left, and down if it eats into the subject.
• Check the preview on light and dark themes at 16, 22 and 32 pixels, then download the PNG.

It works best on a plain background: a logo on white, a photo against a wall, a screenshot of text. For a text emoji, pick Text to emoji and tick transparent next to the background color.

On a Mac

In Finder, right-click the image, choose Quick Actions, then Remove Background. macOS saves a new PNG next to the original with the background cut out. It handles people, pets and objects in photos, not only plain backgrounds.

For more control, open the image in Preview, click the Markup button, choose Instant Alpha (the magic wand), drag over the background until it is selected, and press Delete. Then File, Export, and pick PNG.

On iPhone or iPad

Open the photo in Photos, touch and hold the subject until it lifts off the background, and tap Copy or Share. Save the result as an image; it keeps the transparent background. You can add it as a custom emoji straight from the Slack app on iPhone and iPad; the steps are in how to add custom emoji to Slack.

On Windows 11

Open the image in Paint and click Remove background in the toolbar. Paint cuts out the main subject. Save with File, Save as, PNG picture. The Windows Photos app also has a background tool under Edit.

With ImageMagick

To make white pixels transparent and resize to 128 by 128:

# Replace near-white with transparency, then resize to a 128x128 square
magick input.png -fuzz 10% -transparent white -resize 128x128 -gravity center -background none -extent 128x128 emoji.png

For an animated GIF, work on every frame:

magick input.gif -coalesce -fuzz 10% -transparent white -resize 128x128 -layers optimize emoji.gif

Raise -fuzz if a light halo stays, and lower it if parts of the subject disappear.

Why a Slack emoji still has a white or black edge

AI image tools draw emoji on a white background more often than not; AI Slack emoji generator covers prompts that make the background easy to clear.

Slack emoji size and upload

Keep the finished emoji square, 128 by 128 pixels, and under 128 KB. Animated GIFs can have up to 50 frames. If the file is too big, the Slack emoji resizer shrinks it and keeps the transparency and animation. All the limits are in Slack GIF size limit.

To upload it, click the smiley face in the message field, then Add Emoji, choose the file, give it a name, and Save.

FAQ

Can Slack emoji have a transparent background? Yes. Upload a PNG or GIF with transparent pixels. Slack recommends it.

Why does my Slack emoji have a white background? The image was saved with a white background, often as a JPG. Remove the background and save as PNG.

What is the best format for a Slack emoji? PNG for still emoji, GIF for animated ones. Square, 128 by 128 pixels, under 128 KB.

How do I remove a background for a Slack emoji for free? Use the slack.green emoji maker in the browser, Remove Background in Finder on a Mac, or Paint on Windows 11.