Check any domain's apple-app-site-association file and make sure your iOS Universal Links are set up correctly — hosting, format, structure, and app ID matching, in one click.
We fetch the file server-side (browsers can't cross-origin fetch another domain's AASA file) using our open-source engine. Nothing is stored.
The apple-app-site-association (AASA) file is a small JSON file you host on your domain. It tells iOS which app is allowed to open which URLs — the foundation of Universal Links. When a user taps a link to your site, iOS reads this file to decide whether to open your app or fall back to Safari.
If the file is missing, unreachable, served with the wrong headers, or doesn't list your app, Universal Links silently break and links open the browser instead. The problems are notoriously hard to debug because iOS gives almost no feedback — which is exactly what this validator surfaces.
Every check reports pass, warn, or fail so you know exactly what to fix.
iOS fetches the AASA file over HTTPS and does not follow redirects. Serve it directly from https://yourdomain.com/.well-known/apple-app-site-association with a 200 response.
The file must have no file extension. Content-Type should be application/json (older guidance allowed application/pkcs7-mime for signed files, but modern apps use unsigned JSON).
A stray comma, comment, or a UTF-8 BOM will cause iOS to silently reject the file. Validate the raw bytes are clean JSON.
The appID must be TeamID.BundleID (e.g. ABCDE12345.com.example.app). If it is missing or misspelled, Universal Links will never open your app. Use the advanced fields above to confirm a match.
The old { "applinks": { "apps": [], "details": [{ "appID": ..., "paths": [...] }] } } shape still works, but the modern components-based format is recommended for newer iOS versions.
The apple-app-site-association (AASA) file is a JSON file hosted on your domain that tells iOS which app is allowed to open which URLs. It is the backbone of Universal Links — without a valid AASA file, tapping a link opens Safari instead of your app.
At https://yourdomain.com/.well-known/apple-app-site-association, served over HTTPS, with no redirects and no file extension.
Browsers block cross-origin requests, so a page cannot fetch another domain’s AASA file directly. This tool fetches and validates the file server-side using the open-source @linkforty/aasa-core engine.
Yes. It is a free tool built on LinkForty’s open-source AASA validation engine. No sign-up required.
LinkForty manages your deep links, Universal Links, and attribution — with a hosted AASA file, so links open the right app every time. Track what users do after the click, on web and mobile.
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