Nostr address checker

What a NIP-05 address really is

A NIP-05 address looks like an email address, but it is a verification, not an inbox. The domain publishes a small file at /.well-known/nostr.json mapping names to hex public keys. When a client shows a checkmark next to name@domain.com, it means exactly one thing: that domain currently vouches that this name belongs to that key.

That makes NIP-05 a human readable pointer to a key, with the domain's reputation behind it. It does not make the domain the owner of the identity. Your key remains your identity; the address is a label someone can verify.

Why verification matters

Impersonation on Nostr is cheap: anyone can copy a display name and avatar in a minute. What they cannot copy is a verified address on a domain they do not control. Before you zap someone, follow a project account, or trust a DM, resolving their address and comparing keys is the fastest check available.

This tool fetches the domain's nostr.json directly from your browser and shows you the key it returns, as both hex and npub. Paste the npub you expected in the compare field and you get a clear match or mismatch. A mismatch does not always mean fraud, since people rotate keys and domains change hands, but it always means look closer before trusting.

Common reasons an address fails to resolve

The most frequent failure is CORS: the domain serves the file but without the header that lets browsers read it, so wallet apps can resolve it while a web page cannot. The file can also be missing the specific name, return the wrong content type, or the domain may have let the file go stale after a migration.

If you run your own domain, keeping this file correct is the whole job of NIP-05. If you would rather not, a managed address on a maintained domain does the same work with none of the upkeep.

When you publish your own address, check it from a different network than the one that hosts it, because local DNS and caching can hide breakage from you while the rest of the world sees a missing checkmark. This tool runs from wherever your browser is, which makes it a fair approximation of what other people experience.