Performance fix guide
Excessive JavaScript Execution Time
Total JavaScript execution time on the main thread is excessive, competing with rendering and user interaction handling.
Issue ID: CWV-JS-EXEC-001
Severity: moderate
Impact: Med
Effort: L
Use this article when
- You need deeper remediation guidance than the issue card can show.
- You want CMS-specific steps before handing the fix to a developer.
- You want a repeatable re-check path after shipping the change.
What this issue is
Total JavaScript execution time on the main thread is excessive, competing with rendering and user interaction handling.
Why it matters
Total JavaScript execution time on the main thread is excessive, competing with rendering and user interaction handling. This affects load speed, Core Web Vitals, and how many visitors stay long enough to convert.
How we detect it
- FreeSiteAudit flags this issue when the rule for CWV-JS-EXEC-001 fails and the page evidence points to Performance tool.
- You can usually confirm this by checking the page source or the relevant page settings inside your CMS.
Evidence examples
Check the affected page source, rendered output, or relevant CMS setting to confirm the missing or incorrect element.
How to fix it
- 1Reduce JavaScript bundle size
- 2Defer non-critical script execution
- 3Use code splitting and lazy loading
How to re-check it
- Check Lighthouse "Reduce JavaScript execution time" audit
Related tools
This issue is best verified with the full FreeSiteAudit crawl rather than a single-point mini tool.