<script>

Syntax

<script src="app.js"></script>

Examples

<script src="/js/app.js"></script>

<script>
  console.log("Page loaded");
  document.addEventListener("DOMContentLoaded", () => {
    console.log("DOM ready");
  });
</script>

<script src="/js/analytics.js" defer></script>
<script type="module" src="/js/main.js"></script>

Attributes

• src (URL): Path to an external JavaScript file
• defer (boolean): Delays execution until after the document is parsed, preserving order
• async (boolean): Downloads the script in parallel and executes as soon as it is ready, out of order
• type (module | text/javascript): Specifies the scripting language or module type

Best practices

• Place scripts before the closing </body> tag, or use defer, so they do not block HTML rendering
• Use defer for scripts that need to run in order and depend on the full DOM being parsed
• Use async only for independent scripts where execution order does not matter, like analytics
• Prefer external scripts with src over large inline scripts for better caching and readability

At a glance

Purpose

Structure and meaning for web content

File extension

.html · .htm

Runs in

Web browsers

Usually used with

CSS and JavaScript

Specifications & further reading

• HTML Living Standard

Related HTML documentation