diff --git a/crates/net/rpc/Cargo.toml b/crates/net/rpc/Cargo.toml
index c1b8e1f..b6705ac 100644
--- a/crates/net/rpc/Cargo.toml
+++ b/crates/net/rpc/Cargo.toml
@@ -15,6 +15,7 @@ tokio.workspace = true
 ethlambda-metrics.workspace = true
 tracing.workspace = true
 ethlambda-storage.workspace = true
+ethlambda-types.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 
diff --git a/crates/net/rpc/src/lib.rs b/crates/net/rpc/src/lib.rs
index 9c42a70..d577a70 100644
--- a/crates/net/rpc/src/lib.rs
+++ b/crates/net/rpc/src/lib.rs
@@ -1,7 +1,11 @@
 use std::net::SocketAddr;
 
-use axum::{Json, Router, response::IntoResponse, routing::get};
+use axum::{Json, Router, http::HeaderValue, http::header, response::IntoResponse, routing::get};
 use ethlambda_storage::Store;
+use ethlambda_types::primitives::Encode;
+
+pub(crate) const JSON_CONTENT_TYPE: &str = "application/json; charset=utf-8";
+pub(crate) const SSZ_CONTENT_TYPE: &str = "application/octet-stream";
 
 pub mod metrics;
 
@@ -35,14 +39,32 @@ async fn get_latest_finalized_state(
     let state = store
         .get_state(&finalized.root)
         .expect("finalized state exists");
-    Json(state)
+    ssz_response(state.as_ssz_bytes())
 }
 
 async fn get_latest_justified_state(
     axum::extract::State(store): axum::extract::State<Store>,
 ) -> impl IntoResponse {
     let checkpoint = store.latest_justified();
-    Json(checkpoint)
+    json_response(checkpoint)
+}
+
+fn json_response<T: serde::Serialize>(value: T) -> axum::response::Response {
+    let mut response = Json(value).into_response();
+    response.headers_mut().insert(
+        header::CONTENT_TYPE,
+        HeaderValue::from_static(JSON_CONTENT_TYPE),
+    );
+    response
+}
+
+fn ssz_response(bytes: Vec<u8>) -> axum::response::Response {
+    let mut response = bytes.into_response();
+    response.headers_mut().insert(
+        header::CONTENT_TYPE,
+        HeaderValue::from_static(SSZ_CONTENT_TYPE),
+    );
+    response
 }
 
 #[cfg(test)]
@@ -126,12 +148,15 @@ mod tests {
 
     #[tokio::test]
     async fn test_get_latest_finalized_state() {
+        use ethlambda_types::primitives::Encode;
+
         let state = create_test_state();
         let store = Store::from_genesis(state);
 
-        // Get the expected state from the store to build expected JSON
+        // Get the expected state from the store
         let finalized = store.latest_finalized();
         let expected_state = store.get_state(&finalized.root).unwrap();
+        let expected_ssz = expected_state.as_ssz_bytes();
 
         let app = build_api_router(store);
 
@@ -146,39 +171,12 @@ mod tests {
             .unwrap();
 
         assert_eq!(response.status(), StatusCode::OK);
-
-        let body = response.into_body().collect().await.unwrap().to_bytes();
-        let returned_state: serde_json::Value = serde_json::from_slice(&body).unwrap();
-
-        let header = &expected_state.latest_block_header;
         assert_eq!(
-            returned_state,
-            json!({
-                "config": {
-                    "genesis_time": expected_state.config.genesis_time
-                },
-                "slot": expected_state.slot,
-                "latest_block_header": {
-                    "slot": header.slot,
-                    "proposer_index": header.proposer_index,
-                    "parent_root": format!("{:#x}", header.parent_root),
-                    "state_root": format!("{:#x}", header.state_root),
-                    "body_root": format!("{:#x}", header.body_root)
-                },
-                "latest_justified": {
-                    "slot": expected_state.latest_justified.slot,
-                    "root": format!("{:#x}", expected_state.latest_justified.root)
-                },
-                "latest_finalized": {
-                    "slot": expected_state.latest_finalized.slot,
-                    "root": format!("{:#x}", expected_state.latest_finalized.root)
-                },
-                "historical_block_hashes": [],
-                "justified_slots": "0x01",
-                "validators": [],
-                "justifications_roots": [],
-                "justifications_validators": "0x01"
-            })
+            response.headers().get(header::CONTENT_TYPE).unwrap(),
+            SSZ_CONTENT_TYPE
         );
+
+        let body = response.into_body().collect().await.unwrap().to_bytes();
+        assert_eq!(body.as_ref(), expected_ssz.as_slice());
     }
 }
diff --git a/crates/net/rpc/src/metrics.rs b/crates/net/rpc/src/metrics.rs
index c3edac6..aadb021 100644
--- a/crates/net/rpc/src/metrics.rs
+++ b/crates/net/rpc/src/metrics.rs
@@ -1,4 +1,4 @@
-use axum::{Router, http::HeaderValue, response::IntoResponse, routing::get};
+use axum::{Router, http::HeaderValue, http::header, response::IntoResponse, routing::get};
 use ethlambda_metrics::gather_default_metrics;
 use tracing::warn;
 
@@ -9,7 +9,12 @@ pub fn start_prometheus_metrics_api() -> Router {
 }
 
 pub(crate) async fn get_health() -> impl IntoResponse {
-    r#"{"status": "healthy", "service": "lean-spec-api"}"#
+    let mut response = r#"{"status":"healthy","service":"lean-spec-api"}"#.into_response();
+    response.headers_mut().insert(
+        header::CONTENT_TYPE,
+        HeaderValue::from_static(crate::JSON_CONTENT_TYPE),
+    );
+    response
 }
 
 pub(crate) async fn get_metrics() -> impl IntoResponse {
@@ -20,6 +25,8 @@ pub(crate) async fn get_metrics() -> impl IntoResponse {
         .unwrap_or_default()
         .into_response();
     let content_type = HeaderValue::from_static("text/plain; version=0.0.4; charset=utf-8");
-    response.headers_mut().insert("content-type", content_type);
+    response
+        .headers_mut()
+        .insert(header::CONTENT_TYPE, content_type);
     response
 }