diff --git a/src/snek/system/template.py b/src/snek/system/template.py
index ff3b4c8..6460ff1 100644
--- a/src/snek/system/template.py
+++ b/src/snek/system/template.py
@@ -181,7 +181,7 @@ def enrich_image_rendering(text):
     soup = BeautifulSoup(text, "html.parser")
     for element in soup.find_all("img"):
         if element.attrs["src"].startswith("/"):
-            element.attrs["src"] += "?width=240&height=240"
+            element.attrs["src"] += "?width=240&height=240&format=webp"
             picture_template = f'''
                                 <picture>
                                     <source srcset="{element.attrs["src"]}" type="{mimetypes.guess_type(element.attrs["src"])[0]}" />