diff --git a/.changelog/18367.txt b/.changelog/18367.txt
new file mode 100644
index 0000000000..578cf70918
--- /dev/null
+++ b/.changelog/18367.txt
@@ -0,0 +1,3 @@
+```release-note:bug
+dev-mode: Fix dev mode has new line in responses. Now new line is added only when url has pretty query parameter.
+```
diff --git a/agent/http.go b/agent/http.go
index 31aaf68c20..200f28c755 100644
--- a/agent/http.go
+++ b/agent/http.go
@@ -616,7 +616,9 @@ func (s *HTTPHandlers) marshalJSON(req *http.Request, obj interface{}) ([]byte,
 		if err != nil {
 			return nil, err
 		}
-		buf = append(buf, "\n"...)
+		if ok {
+			buf = append(buf, "\n"...)
+		}
 		return buf, nil
 	}