What you can actually make yourself
You cannot create a true emoji — the small pictures that appear in your phone's keyboard and work across all apps and devices. Those are controlled by Unicode, a standards organization that releases new official emojis once or twice a year. What you can make are custom images that look and work like emojis in specific places: custom reactions in Slack, stickers in iMessage or WhatsApp, or reaction sets in Discord.
The difference matters because a real emoji works everywhere — your text message, your email, someone else's phone, a website. A custom image only works in the app where you uploaded it. But for everyday use, custom images do the same job: they let you add a personal picture to a message instead of picking from the standard set.
The easiest route depends on which app you use most. If you are in Slack at work, you can upload a custom emoji in under a minute. If you text friends on iMessage, you can create stickers. If you use Discord, you can add custom emojis to your server. Each one uses different tools and has different limits.
Key Takeaways
- Official emojis come from Unicode and work everywhere; custom images only work in specific apps like Slack, Discord, or iMessage.
- Slack lets you upload PNG or GIF files up to 128 × 128 pixels as custom emojis that your workspace can use.
- iMessage stickers can be created in Sticker Pack format using Xcode on Mac, or you can use third-party apps like Sticker Maker Studio to create them faster.
- Discord custom emojis must be under 256 KB and work only in the server where you uploaded them, not across Discord as a whole.
- You need admin or moderator permissions in Slack, Discord, or iMessage to upload custom images for group use.
Creating custom emojis in Slack
Slack is the fastest place to add a custom emoji if you have admin access. Go to your workspace settings, find "Customize Slack," then click "Emoji." You can upload a PNG, GIF, JPG, or BMP file. The image should be square and at least 128 × 128 pixels — larger files will be shrunk down. Slack accepts files up to 64 MB, though most emoji images are much smaller.
Once you upload the file, you give it a name — something like "thumbsup-cat" or "coffee-break." That name is what people type when they search for your emoji in the message box. You can also set an alias, a second name that does the same thing. After you save it, anyone in your workspace can use it by typing a colon, the name, and another colon (like :thumbsup-cat:) or by clicking the emoji picker and searching for it.
The catch is that you need admin or owner permissions to add custom emojis. If you do not have those, you can ask your workspace admin to add it for you, or you can create your own Slack workspace for free and add as many custom emojis as you want.
Making stickers for iMessage on iPhone or Mac
iMessage stickers are small animated or static images you can add to messages. The official way to create them is through Xcode, Apple's free development tool for Mac. You create a sticker pack — a folder of PNG images, usually 300 × 300 pixels or 408 × 408 pixels — and Xcode packages them into a format iMessage recognizes. This route takes time and requires learning Xcode basics.
A faster alternative is to use a third-party app like Sticker Maker Studio (available on the Mac App Store) or Unfolder. These apps let you upload images, resize them, and export them as iMessage sticker packs without touching code. You design your stickers in any image editor — Photoshop, Canva, or even Preview on Mac — then import them into the sticker app.
Once your sticker pack is ready, you can share it with friends through iMessage, or you can submit it to the App Store as a standalone sticker app. If you submit to the App Store, Apple reviews it first, and other people can read it. If you just share it with friends, only they can use it.
Adding custom emojis to a Discord server
Discord lets you upload custom emojis that only work in your server. You need to be the server owner or have the "Manage Emoji" permission. Go to Server Settings, click "Emoji," then "Upload Emoji." You can upload a PNG, GIF, JPG, or WEBP file up to 256 KB. The image should be square — Discord recommends 128 × 128 pixels or larger, up to 1024 × 1024 pixels.
Give your emoji a name (like "partyparrot" or "coffee"), and it will be available to everyone in that server. They can use it by typing a colon and the name, or by clicking the emoji picker. Unlike Slack, Discord emojis do not work in other servers or in direct messages — they only work in the server where you uploaded them.
Discord servers have limits: free servers can have up to 50 custom emojis, and servers with a paid boost can have more. If you hit the limit, you have to delete old emojis to add new ones.
Using online emoji makers for quick images
If you want to create an emoji-style image without learning design software, online tools like Bitmoji, Emoji Kitchen, or Picrew let you build a character or image quickly. Bitmoji creates a cartoon version of you that you can customize with different expressions and poses. Emoji Kitchen (made by Google) lets you combine two existing emojis into a new one. Picrew is a collection of character creators where you can build a custom avatar.
These tools export as PNG or GIF files, which you can then upload to Slack, Discord, or use in an iMessage sticker pack. They are useful if you want something that looks polished but do not want to design from scratch. The downside is that the results look similar to other people using the same tool — your Bitmoji will look like thousands of other Bitmojis.
What size and format to use for each platform
| Platform | Recommended Size | File Format | File Size Limit |
|---|---|---|---|
| Slack | 128 × 128 pixels (minimum) | PNG, GIF, JPG, BMP | 64 MB |
| Discord | 128 × 128 to 1024 × 1024 pixels | PNG, GIF, JPG, WEBP | 256 KB |
| iMessage Stickers | 300 × 300 or 408 × 408 pixels | PNG (static or animated) | No strict limit per image |
The key difference is that Discord has a tight file size limit (256 KB), so you may need to compress your image. Slack is more forgiving. iMessage stickers can be larger and more detailed because they are not constrained by the same limits.
Frequently Asked Questions
Can I use someone else's image to make a custom emoji?
Technically yes, but you should not. If you upload an image you did not create or do not have permission to use, you could violate copyright. Stick to images you made yourself, images with a Creative Commons license that allows reuse, or images from free stock sites like Unsplash or Pexels.
Will my custom emoji work if I send it to someone outside my Slack workspace or Discord server?
No. Custom emojis only work within the app and space where you uploaded them. If you send a message with a custom emoji to someone outside your workspace, they will see a broken image or a code instead of the picture. This is why custom emojis are best for group chats or team spaces where everyone is in the same app.
Can I animate my custom emoji?
Yes, if you use a GIF file. Slack, Discord, and iMessage all support animated GIFs. The GIF should still meet the size and dimension requirements for each platform. Keep animations short — a few seconds is enough.
What if I want to make a real emoji that works everywhere?
You cannot submit your own emoji to Unicode directly. Unicode accepts proposals from organizations and individuals, but the process takes months and requires a detailed proposal explaining why the emoji is needed. For most people, a custom emoji in Slack or Discord is the practical solution.
Do I need special software to create the image itself?
No. You can use any image editor: Photoshop, GIMP (free), Canva (free online), or even Microsoft Paint. The image just needs to be saved as PNG, GIF, or JPG. If you have no design experience, Canva has emoji templates you can customize in minutes.