Performance Recommended

Never let a script block the page

Load scripts as type="module" or with defer, keep blocking scripts out of the head, and send as little JavaScript as possible.

By Erik Bergstedt, Agent Wranglers. Updated 20 October 2026.

How to do it

Ship one type="module" bundle, which is deferred by default. Keep inline scripts to tiny ones that must run before paint, such as applying a saved theme. Load third-party code late, or not at all.

Example

<head>
  <script>
    try { document.documentElement.dataset.theme = localStorage.theme || ""; } catch {}
  </script>
  <script type="module" src="/app.3f9a1c.js"></script>
</head>

How to check

Total Blocking Time is near 0. Nothing blocks the parser.

For agents: if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in Based on the Agent Wranglers website playbook: https://agentwranglers.se/playbook/website/performance/script-loading.