NIP-21

nostr: links

NIP-21 defines nostr: links, which let profiles, notes, and other Nostr objects be opened from websites or other apps. A link can point to a Nostr identity or event without depending on a single social-media website.

For users, this is the difference between “open this on one company's site” and “open this in whatever Nostr app you prefer.” It helps Nostr content behave more like email links or phone links.

Read more in the official 21.md NIP document.