diff --git a/21.md b/21.md
index 988485d..843112e 100644
--- a/21.md
+++ b/21.md
@@ -18,3 +18,14 @@ The identifiers that come after are expected to be the same as those defined in
 - `nostr:nprofile1qqsrhuxx8l9ex335q7he0f09aej04zpazpl0ne2cgukyawd24mayt8gpp4mhxue69uhhytnc9e3k7mgpz4mhxue69uhkg6nzv9ejuumpv34kytnrdaksjlyr9p`
 - `nostr:note1fntxtkcy9pjwucqwa9mddn7v03wwwsu9j330jj350nvhpky2tuaspk6nqc`
 - `nostr:nevent1qqstna2yrezu5wghjvswqqculvvwxsrcvu7uc0f78gan4xqhvz49d9spr3mhxue69uhkummnw3ez6un9d3shjtn4de6x2argwghx6egpr4mhxue69uhkummnw3ez6ur4vgh8wetvd3hhyer9wghxuet5nxnepm`
+
+# Typed Schemes
+
+Nostr apps SHOULD register for the specific event types they support, enabling operating systems to suggest only applications that can handle those event types and allowing the OS to have a different default application for each type.
+
+The typed scheme is `nostr<event type number>:` followed by a `note`, `nevent` or an `naddr` [NIP-19](19.md) identifier.
+
+## Examples
+
+- `nostr1:note1fntxtkcy9pjwucqwa9mddn7v03wwwsu9j330jj350nvhpky2tuaspk6nqc`
+- `nostr1:nevent1qqstna2yrezu5wghjvswqqculvvwxsrcvu7uc0f78gan4xqhvz49d9spr3mhxue69uhkummnw3ez6un9d3shjtn4de6x2argwghx6egpr4mhxue69uhkummnw3ez6ur4vgh8wetvd3hhyer9wghxuet5nxnepm`