AASA Validator

Why this matters

iOS Universal Links break silently. When they work, tapping a link opens your app; when they don't, it quietly falls back to Safari and nobody gets an error. The thing that decides which happens is a single JSON file — the apple-app-site-association (AASA) file — hosted at /.well-known/ on your domain. Get one detail wrong and links stop opening your app, with almost no feedback from iOS to tell you why.

And there are a lot of details to get wrong: it has to be served over HTTPS, with no redirects, no file extension, the right content type, valid JSON with no stray byte-order mark, and your app ID spelled exactly right inside it. Miss any one and Universal Links fail.

The AASA Validator checks all of it for you, in one click — for free.

What it does

Enter a domain and the validator fetches its AASA file and runs the full checklist, reporting every check as pass, warn, or fail so you know exactly what to fix:

• Hosting — domain reachable, served over HTTPS, found at /.well-known/apple-app-site-association, returns a 200, and follows no redirects.
• Format — correct content type, no file extension, valid JSON, no byte-order mark, reasonable size.
• Structure — recognized top-level keys, a valid applinks shape (both modern and legacy formats), and well-formed app ID and component patterns.
• Identifier — optionally supply your App ID (or Team ID + Bundle ID) and it confirms your app is actually listed. This catches the single most common Universal Links mistake: a perfectly valid file that just doesn't include your app.

How it works

Browsers can't fetch another domain's AASA file — cross-origin requests are blocked — so the validator does the fetch and validation server-side. It's powered by @linkforty/aasa-core, our open-source, zero-dependency validation engine, which is MIT-licensed and free to use in your own projects. Nothing you enter is stored.

LinkForty handles this for you

The validator is a free standalone tool — no LinkForty account needed. But if you'd rather not maintain an AASA file at all, that's exactly what LinkForty does: we host a correct, always-valid association file for your links, so Universal Links open the right app every time — and then track what the user does after the click, on web and mobile.

Try it

Open the AASA Validator and check your domain. It's free, no sign-up, and takes about five seconds.