diff --git a/Contributing.md b/Contributing.md
index 94644c0..39a2ed0 100644
--- a/Contributing.md
+++ b/Contributing.md
@@ -93,7 +93,7 @@ The reference tests require you to generate original snapshots for comparison. T
 ```
 cp test/resources/browser_manifests/browser_manifest.json.example test/resources/browser_manifests/browser_manifest.json
 ```
-Then edit the manifest and make sure it points to the browser(s) you want to use for generating the reference images.
+Then edit the manifest and make sure it points to the browser(s) you want to use for generating the reference images. Optionally, you can add `"headless": true` to entries to disable showing the GUI of the browser.
 
 Now we can generate the reference images: