diff --git a/backend/cmd/api/json.go b/backend/cmd/api/json.go
new file mode 100644
index 0000000..c6d93fb
--- /dev/null
+++ b/backend/cmd/api/json.go
@@ -0,0 +1,20 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+)
+
+func writeJSON(w http.ResponseWriter, status int, data any) error {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(status)
+	return json.NewEncoder(w).Encode(data)
+}
+
+func writeJSONError(w http.ResponseWriter, status int, message string) error {
+	type envelope struct {
+		Error string `json:"error"`
+	}
+
+	return writeJSON(w, status, &envelope{Error: message})
+}