Deep Link Debugger
Paste a domain to validate its Universal Links and Android App Links. We fetch your apple-app-site-association and assetlinks.json, show the parsed JSON, and flag the errors that quietly break deep links.
What this checks
Universal-link hell is almost always one of a handful of small mistakes. Here's everything the debugger validates for you.
iOS · apple-app-site-association
- Served at /.well-known/ over HTTPS with a 200
- No redirects (iOS won't follow them)
- Content-Type is application/json
- Valid JSON, no BOM, under the 128 KB limit
- applinks.details with appIDs / paths / components
- App ID has a valid 10-character Team ID prefix
Android · assetlinks.json
- Served at /.well-known/ over HTTPS with a 200
- No redirects on the verification request
- Content-Type is application/json
- Valid JSON array of statements
- delegate_permission/common.handle_all_urls relation
- package_name + well-formed SHA-256 fingerprints
Universal Link & App Link FAQ
Why aren't my Universal Links opening the app?+
The most common causes are: the apple-app-site-association file isn't served at /.well-known/ over HTTPS with a 200 response, it's returned through a redirect (iOS won't follow it), it's served with the wrong Content-Type, the JSON is invalid, or the App ID is missing the 10-character Team ID prefix. This tool checks all of these.
Where should the apple-app-site-association file live?+
At https://yourdomain.com/.well-known/apple-app-site-association, served over HTTPS with a valid certificate, no redirect, and no file extension. Since iOS 9.3 the .well-known path is required.
Does the AASA file need to be application/json?+
Apple recommends serving it as application/json. Modern iOS is more lenient, but a text/html Content-Type (often an HTML error page in disguise) is a frequent cause of silent failures, so we flag it.
What breaks Android App Links most often?+
A missing or malformed SHA-256 certificate fingerprint, the wrong package_name, missing the delegate_permission/common.handle_all_urls relation, a redirect on the assetlinks.json request, or the file not being valid JSON. If you use Play App Signing, copy the fingerprint from the Play Console — not your local keystore.
Is this tool free? Do I need to sign up?+
It's completely free and requires no login. Paste a domain and get results instantly.
More free tools: AASA & assetlinks.json generator · Firebase Dynamic Links migration checker · UTM builder
Learn more: What is deep linking · Deferred deep linking · Deep linking for mobile apps