Use async or defer attributes for JavaScript to prevent render blocking.
- Use async or defer attributes for JavaScript to prevent render blocking1 cited source1 category
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Why this matters
Loading JavaScript without blocking rendering improves page interactivity and speed.
Hypothetical standard operating procedure
Adapt this example to your site, access, tools, and change process. It is our suggested procedure, informed by the sources below.
- Add async attribute to scripts that do not depend on DOM or other scripts.
- Use defer for scripts that require DOM but not blocking parsing.
- Place scripts at the end of the body or after critical DOM elements.
- Test page load performance and interaction readiness timings.
- Avoid inline scripts that block rendering unless critical.
Watch for
Synchronous script loading blocks rendering and delays page interactivity.
Definition of done
JavaScript loads without blocking initial page render, verified by faster content paint times.
Sources & attribution
Original checklist wording and example SOP by Best SEO Checklist, using source-grounded AI assistance. Editorial contact: Ted Kubaitis, @tedkubaitis on Teams. Check current source guidance before implementation.