diff --git a/masque/file/svg.py b/masque/file/svg.py
index 859c074..7c77fd9 100644
--- a/masque/file/svg.py
+++ b/masque/file/svg.py
@@ -20,6 +20,7 @@ def writefile(
         top: str,
         filename: str,
         custom_attributes: bool = False,
+        annotate_ports: bool = False,
         ) -> None:
     """
     Write a Pattern to an SVG file, by first calling .polygonize() on it
@@ -44,6 +45,8 @@ def writefile(
         filename: Filename to write to.
         custom_attributes: Whether to write non-standard `pattern_layer` attribute to the
             SVG elements.
+        annotate_ports: If True, draw an arrow for each port (similar to
+            `Pattern.visualize(..., ports=True)`).
     """
     pattern = library[top]
 
@@ -79,6 +82,27 @@ def writefile(
 
                     svg_group.add(path)
 
+        if annotate_ports:
+            # Draw arrows for the ports, pointing into the device (per port definition)
+            for port_name, port in pat.ports.items():
+                if port.rotation is not None:
+                    p1 = port.offset
+                    angle = port.rotation
+                    size = 1.0  # arrow size
+                    p2 = p1 + size * numpy.array([numpy.cos(angle), numpy.sin(angle)])
+
+                    # head
+                    head_angle = 0.5
+                    h1 = p1 + 0.7 * size * numpy.array([numpy.cos(angle + head_angle), numpy.sin(angle + head_angle)])
+                    h2 = p1 + 0.7 * size * numpy.array([numpy.cos(angle - head_angle), numpy.sin(angle - head_angle)])
+
+                    line = svg.line(start=p1, end=p2, stroke='green', stroke_width=0.2)
+                    head = svg.polyline(points=[h1, p1, h2], fill='none', stroke='green', stroke_width=0.2)
+
+                    svg_group.add(line)
+                    svg_group.add(head)
+                    svg_group.add(svg.text(port_name, insert=p2, font_size=0.5, fill='green'))
+
         for target, refs in pat.refs.items():
             if target is None:
                 continue