# Universal Links
> Set up and test universal links for iOS using setup-safari
- Skill: `evanbacon/universal-links` (Agent Skill)
- Install (CLI): `npx skillmds@latest add evanbacon/universal-links`
- Raw SKILL.md: https://api.skillmd.com/api/skills/evanbacon/universal-links/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: evanbacon (https://skillmd.com/u/evanbacon)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/evanbacon/universal-links
---
Use `bunx setup-safari` to configure and test universal links (deep links) on iOS.
## Important: When Custom Builds Are Needed
**Universal links with custom domains require custom native builds.** Your app will no longer work in Expo Go.
However, for basic deep linking during development:
- **Expo Go supports** the `exp://` URL scheme and Expo-hosted URLs
- **Custom builds required** for your own domain's universal links (applinks:yourdomain.com)
If you only need deep linking for development/testing, try `npx expo start` with Expo Go first. Only create custom builds when you need production universal links with your own domain.
## Automated Setup (Recommended)
Run setup-safari with your Apple ID to automate credential lookup:
```bash
EXPO_APPLE_ID="your-apple-id@email.com" bunx setup-safari
```
This will:
1. Authenticate with Apple Developer Portal
2. Enable Associated Domains for your bundle ID
3. Output the AASA file content and meta tag
**After running, you must manually:**
### 1. Create the AASA file
Create `public/.well-known/apple-app-site-association` (no file extension):
```json
{
"applinks": {
"details": [
{
"appIDs": ["TEAM_ID.com.your.bundleid"],
"components": [
{
"/": "*",
"comment": "Matches all routes"
}
]
}
]
},
"activitycontinuation": {
"apps": ["TEAM_ID.com.your.bundleid"]
},
"webcredentials": {
"apps": ["TEAM_ID.com.your.bundleid"]
}
}
```
### 2. Create src/app/+html.tsx with Smart App Banner
```tsx
import { ScrollViewStyleReset } from "expo-router/html";
export default function Root({ children }: { children: React.ReactNode }) {
return (
{children}
);
}
```
### 3. Add Associated Domains to app.json
```json
{
"expo": {
"ios": {
"associatedDomains": [
"applinks:yourdomain.com",
"activitycontinuation:yourdomain.com",
"webcredentials:yourdomain.com"
]
}
}
}
```
### 4. Deploy and Rebuild
```bash
# Deploy web (AASA file must be accessible)
npx expo export -p web && npx eas-cli deploy
# Rebuild iOS app with new entitlements
npx expo run:ios
# Or for TestFlight: npx testflight
```
## Interactive Setup (Alternative)
For interactive mode (requires TTY):
```bash
bunx setup-safari
```
## How Universal Links Work
Universal links require two parts:
1. **AASA file on your server** - Tells iOS which paths your app handles
2. **Associated Domains entitlement** - Tells your app which domains to claim
## AASA File Format
Host at `https://yourdomain.com/.well-known/apple-app-site-association`:
```json
{
"applinks": {
"apps": [],
"details": [
{
"appID": "TEAM_ID.com.example.app",
"paths": ["*"]
}
]
}
}
```
Path patterns:
- `*` - Match all paths
- `/products/*` - Match paths starting with /products/
- `/item/???` - Match exactly 3 characters after /item/
- `NOT /admin/*` - Exclude paths
## Associated Domains Entitlement
In your `app.json` or `app.config.js`:
```json
{
"expo": {
"ios": {
"associatedDomains": [
"applinks:yourdomain.com",
"applinks:www.yourdomain.com"
]
}
}
}
```
## Testing Universal Links
After setup, test with setup-safari:
```bash
npx setup-safari
```
Or manually test in Safari:
1. Open Safari on iOS device/simulator
2. Navigate to a URL that should open your app
3. Pull down to reveal the banner, or long-press the link
## Testing with Tunnel (No Server Required)
Test universal links without deploying a website using Expo's tunnel feature:
1. **Set a consistent tunnel subdomain:**
```bash
export EXPO_TUNNEL_SUBDOMAIN=my-app-name
```
2. **Configure associated domains with the ngrok URL:**
```json
{
"expo": {
"ios": {
"associatedDomains": ["applinks:my-app-name.ngrok.io"]
}
}
}
```
3. **Build the development client:**
```bash
npx expo run:ios
```
4. **Start the dev server with tunnel:**
```bash
npx expo start --tunnel
```
5. **Test the link** - Type `https://my-app-name.ngrok.io` in Safari on your device. It should open your app directly.
The tunnel creates a public HTTPS URL that serves the AASA file automatically, letting you test the full universal links flow during development.
## Debugging
Check if Apple has cached your AASA:
```bash
curl "https://app-site-association.cdn-apple.com/a/v1/yourdomain.com"
```
Validate AASA file format:
```bash
curl https://yourdomain.com/.well-known/apple-app-site-association | jq
```
Common issues:
- AASA must be served with `Content-Type: application/json`
- HTTPS required (no self-signed certs)
- Apple caches AASA files - changes may take time to propagate
## Expo Router Integration
With Expo Router, handle incoming links automatically:
```tsx
// app/[...path].tsx handles all deep link paths
// app/products/[id].tsx handles /products/:id links
```
Access link parameters:
```tsx
import { useLocalSearchParams } from "expo-router";
export default function Product() {
const { id } = useLocalSearchParams();
return Product: {id};
}
```