diff --git a/docs/nip78.md b/docs/nip78.md
new file mode 100644
index 0000000..043ec45
--- /dev/null
+++ b/docs/nip78.md
@@ -0,0 +1,7 @@
+# Ditto NIP-78 events
+
+[NIP-78](https://github.com/nostr-protocol/nips/blob/master/78.md) defines events of kind `30078` with a globally unique `d` tag. These events are queried by the `d` tag, which allows Ditto to store custom data on relays. Ditto uses reverse DNS names like `pub.ditto.<thing>` for `d` tags.
+
+## `pub.ditto.blocks`
+
+An encrypted array of blocked pubkeys, JSON stringified and encrypted with `nip07.encrypt`.
\ No newline at end of file