Custom emoji (recommended)
Recommended128×128 1:1
Practical custom emoji upload. Keep the glyph bold—tiny detail disappears.
Use in toolSlack · Image size
Slack Emoji Size
Custom Slack emoji upload as small squares. Export 128×128 with a bold center mark, then download.
Browser crop · stays on your device
Crop your Slack custom emoji
128 × 128
Add a photo to crop
Upload a bold glyph—or try the sample—then keep the mark inside the readable center before you download.
Size specs
This is a reaction / shortcut glyph—not a 512×512 workspace icon and not a profile photo.
Publish
Export this for Slack upload.
| Asset | Pixels | Ratio | Notes | Action |
|---|---|---|---|---|
| Custom emoji (recommended) Recommended | 128×128 | 1:1 | Practical custom emoji upload. Keep the glyph bold—tiny detail disappears. | Use in tool |
Custom emoji are postage stamps in the picker
Custom emoji appear in the Slack emoji picker, as message reactions, and when someone types a :shortcut:. At 128×128, thin lines, long wordmarks, and photo backgrounds vanish. Design like a sticker, not like a billboard.
Do not upload a 512×512 workspace icon and hope Slack downscales cleanly. Icons have different margins and detail density. Crop—or better, redraw—a dedicated glyph with a clear silhouette and high contrast against both light and dark themes.
Animated GIF rules vary by workspace plan and admin settings. This tool exports still frames (JPG/PNG). If your workspace allows animated emoji, prepare the GIF in a separate editor at the same square habit, then keep file weight low.
Name the shortcut carefully after upload (:shipit:, :launch:, etc.). The pixel file is only half the job—discoverability in the picker depends on a memorable name and a glyph people can recognize without reading.
Good vs weak crop
Same feed frame—keep the subject inside the margin phones actually show.
Bold reaction stamp
- True 128×128
- Simple silhouette
- High contrast
- Readable as a reaction
Muddy shrink or micro text
- Workspace logo dumped in
- Paragraph of tiny type
- Busy photo background
- Detail lost after downscale
Before you upload
Tick these off against your crop preview—nothing is saved.
Related surfaces compared
Similar-looking slots often use different ratios—do not reuse one export for all of them.
Custom emoji
128 × 128
This page. Reaction / shortcut glyph.
Workspace icon
512 × 512
Team switcher—too detailed to shrink blindly.
Profile picture
512 × 512
Personal circle—not a reaction.
Discord emoji habit
Often 128 × 128
Similar stamp size—re-export per app.
| Surface | Typical size | Note |
|---|---|---|
| Custom emoji | 128 × 128 | This page. Reaction / shortcut glyph. |
| Workspace icon | 512 × 512 | Team switcher—too detailed to shrink blindly. |
| Profile picture | 512 × 512 | Personal circle—not a reaction. |
| Discord emoji habit | Often 128 × 128 | Similar stamp size—re-export per app. |
Design for silhouette, not detail
At reaction size, shape and color carry the meaning. Drop fine textures, small type, and multi-panel comics. One object or face works; a collage does not.
- Prefer flat color and thick strokes.
- Leave transparent or solid margins—do not bleed to every edge if Slack softens corners.
- Check the glyph next to default Slack emoji for scale.
Still frames vs animated GIF
Many workspaces only allow still emoji, or cap GIF size. This crop tool is built for still masters. If animation is allowed, keep the same 128×128 habit and a short loop so the picker stays responsive.
- Ask an admin before relying on animated emoji.
- Keep GIF weight low for mobile Slack.
- Always have a still fallback.
File requirements
PNG is ideal for hard-edged glyphs and transparency. JPG suits photo-based stamps. Prefer sRGB. Export exactly 128×128—do not upload a huge canvas and hope.
- Primary size
- 128 × 128 px
- Aspect
- 1:1
- Formats
- PNG preferred; JPG OK; GIF plan-dependent
- Not workspace icon
- 512 × 512 is a different job
- Best for
- Reactions, shortcuts, picker
Common mistakes
- Dumping the workspace logo into the emoji uploader unchanged.
- Microscopic slogans nobody can read as a reaction.
- Busy photos that turn to noise at 128px.
- Huge source files that Slack rejects or compresses poorly.
How to use the crop tool
Upload a bold graphic, keep Custom emoji (128×128) selected, drag until the glyph sits in the readable center, then download. Cropping stays in the browser.
- Zoom until the silhouette fills the zone.
- Prefer PNG for clean edges.
- Upload in Slack Customize → Emoji yourself.
After you download
From this download to a live upload in a few minutes.
- 1
Download the 128×128 PNG (preferred for hard edges) or JPG from the tool.
- 2
In Slack, open Customize workspace → Emoji → Add emoji (permission required) and upload.
- 3
Set a clear :name: and test as a reaction in a channel.
- 4
If the glyph muddies, simplify the silhouette and re-export.
Frequently asked questions
What size are Slack custom emoji in 2026?
Export a 128×128 square. Keep the glyph bold—tiny detail disappears in the picker and as reactions.
Can I use my Slack workspace icon as a custom emoji?
Not well. Redesign or re-crop a dedicated 128×128 glyph instead of blindly shrinking the 512×512 icon.
Does Slack allow animated custom emoji?
It depends on workspace plan and admin settings. This tool exports stills; prepare GIFs separately if your workspace allows them.
Who can add Slack custom emoji?
Usually members with emoji permission, or admins. Exact rules vary by workspace.
Can I crop Slack emoji in the browser?
Yes. This guide includes an in-browser crop—files stay on your device until you download and upload yourself.