diff --git a/src/nostr.rs b/src/nostr.rs
index 058dad2..3b20711 100644
--- a/src/nostr.rs
+++ b/src/nostr.rs
@@ -4,7 +4,7 @@ use crate::reply::{NostrReply, NostrReplyPrefix};
 use crate::WebSocketService;
 use hyper_tungstenite::tungstenite::Message;
 use pocket_types::json::{eat_whitespace, json_unescape, verify_char};
-use pocket_types::{Event, Filter, Kind, OwnedFilter, Pubkey, Time};
+use pocket_types::{Event, Filter, Hll8, Kind, OwnedFilter, Pubkey, Time};
 use url::Url;
 
 impl WebSocketService {
@@ -170,7 +170,18 @@ impl WebSocketService {
             events.dedup();
 
             if count {
-                let reply = NostrReply::Count(subid, events.len());
+                // HyperLogLog count
+                let mut opthll: Option<Hll8> = None;
+                if filters.len() == 1 {
+                    if let Ok(Some(offset)) = filters[0].hyperloglog_offset() {
+                        let mut hll8 = Hll8::new();
+                        for event in events.iter() {
+                            hll8.add_element(event.pubkey().as_bytes(), offset)?;
+                        }
+                        opthll = Some(hll8);
+                    }
+                }
+                let reply = NostrReply::Count(subid, events.len(), opthll);
                 self.send(Message::text(reply.as_json())).await?;
             } else {
                 for event in events.drain(..) {
diff --git a/src/reply.rs b/src/reply.rs
index 075996d..056b111 100644
--- a/src/reply.rs
+++ b/src/reply.rs
@@ -1,4 +1,4 @@
-use pocket_types::{Event, Id};
+use pocket_types::{Event, Hll8, Id};
 use std::fmt;
 
 pub enum NostrReplyPrefix {
@@ -36,7 +36,7 @@ pub enum NostrReply<'a> {
     Eose(&'a str),
     Closed(&'a str, NostrReplyPrefix, String),
     Notice(String),
-    Count(&'a str, usize),
+    Count(&'a str, usize, Option<Hll8>),
 }
 
 impl NostrReply<'_> {
@@ -50,7 +50,14 @@ impl NostrReply<'_> {
                 format!(r#"["CLOSED","{subid}","{prefix}{msg}"]"#)
             }
             NostrReply::Notice(msg) => format!(r#"["NOTICE","{msg}"]"#),
-            NostrReply::Count(subid, c) => format!(r#"["COUNT","{subid}",{{"count":{c}}}"#),
+            NostrReply::Count(subid, c, opthll) => {
+                if let Some(hll) = opthll {
+                    let hll = hll.to_hex_string();
+                    format!(r#"["COUNT","{subid}",{{"count":{c}, "hll":"{hll}"}}]"#)
+                } else {
+                    format!(r#"["COUNT","{subid}",{{"count":{c}}}]"#)
+                }
+            }
         }
     }
 }