diff --git a/src/deps.ts b/src/deps.ts
index fa7ff6f..53a07e9 100644
--- a/src/deps.ts
+++ b/src/deps.ts
@@ -91,6 +91,8 @@ export {
   type LNURLDetails,
   type MapCache,
   NIP05,
+  type NostrEvent,
+  type NostrFilter,
 } from 'https://gitlab.com/soapbox-pub/nlib/-/raw/5d711597f3b2a163817cc1fb0f1f3ce8cede7cf7/mod.ts';
 
 export type * as TypeFest from 'npm:type-fest@^4.3.0';
diff --git a/src/interfaces/DittoEvent.ts b/src/interfaces/DittoEvent.ts
new file mode 100644
index 0000000..ed327d4
--- /dev/null
+++ b/src/interfaces/DittoEvent.ts
@@ -0,0 +1,24 @@
+import { type NostrEvent } from '@/deps.ts';
+
+/** Ditto internal stats for the event's author. */
+export interface AuthorStats {
+  followers_count: number;
+  following_count: number;
+  notes_count: number;
+}
+
+/** Ditto internal stats for the event. */
+export interface EventStats {
+  replies_count: number;
+  reposts_count: number;
+  reactions_count: number;
+}
+
+/** Internal Event representation used by Ditto, including extra keys. */
+export interface DittoEvent extends NostrEvent {
+  author?: DittoEvent;
+  author_stats?: AuthorStats;
+  event_stats?: EventStats;
+  d_author?: DittoEvent;
+  user?: DittoEvent;
+}
diff --git a/src/interfaces/DittoFilter.ts b/src/interfaces/DittoFilter.ts
new file mode 100644
index 0000000..4ecda96
--- /dev/null
+++ b/src/interfaces/DittoFilter.ts
@@ -0,0 +1,14 @@
+import { type NostrEvent, type NostrFilter } from '@/deps.ts';
+
+import { type DittoEvent } from './DittoEvent.ts';
+
+/** Additional properties that may be added by Ditto to events. */
+export type DittoRelation = Exclude<keyof DittoEvent, keyof NostrEvent>;
+
+/** Custom filter interface that extends Nostr filters with extra options for Ditto. */
+export interface DittoFilter extends NostrFilter {
+  /** Whether the event was authored by a local user. */
+  local?: boolean;
+  /** Additional fields to add to the returned event. */
+  relations?: DittoRelation[];
+}