diff --git a/docs/conf.py b/docs/conf.py
index 4a5ca8069ec4..91a50c51a3a1 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -77,6 +77,7 @@ html_logo = os.path.join(
     topsrcdir, "browser/branding/nightly/content/firefox-wordmark.svg"
 )
 html_favicon = os.path.join(topsrcdir, "browser/branding/nightly/firefox.ico")
+html_js_files = ["https://cdnjs.cloudflare.com/ajax/libs/mermaid/8.9.1/mermaid.js"]
 
 exclude_patterns = ["_build", "_staging", "_venv"]
 pygments_style = "sphinx"