JavaScript Performance Checker
Check how much a URL is loaded by external scripts, inline code, and third-party JavaScript.
Technical pre-testing without browser rendering. Own scores of 0–100 mean: higher = less recognized risk signals. No measured LCP, INP or CLS values. TTFB is measured on the server side.
Ideal for INP optimization, theme checks, tag manager cleanup and front-end budgeting.
Results
Technical pre-checking of a URL. For a crawl over many URLs, use the premium audit.
Findings
Detailed hit
Practical example · for illustration
Loading a rarely used library only when needed
Example: A large chart library is loaded on all pages, although only the statistics module needs it. Limit the import to the affected page or reload the module when used.
What does not prove the result
The known JS size comes from the limited resource testing. Dynamic imports and reloaded files may be missing. Use browser coverage and interaction profiles for confirmation.
Deepen with PageSpeed Insights and available field data · Google's Definition of Core Web Vitals
What the JavaScript Performance Checker evaluated
The pre-check evaluates the retrieved HTML and a limited sample of linked resources. It does not execute JavaScript and does not simulate user interactions. Findings are concrete occasions for an examination in the browser; an inconspicuous result does not exclude performance problems.
From a single check to Core Web Vitals Audit
The audit examines multiple URLs and helps to find recurring technical patterns in templates. This way you can see if a change affects several pages and where you can start the implementation.
Questions about JavaScript Performance Checker
Why is a lot of JavaScript problematic?
JavaScript must be loaded, parsed and executed. This can put a strain on interactions, main thread and battery life.
Does the tool show unused code?
No. It shows load and structure signals. Unused code should be additionally checked in the browser profile.
Why are there standalone tools in addition to the audit?
Individual tools help with a specific URL or technical problem. The audit compares these signals across multiple URLs and shows recurring patterns.
Is the individual check free of charge?
Yes. The standalone tools check a single URL. For larger crawls, complete tables and CSV export, the premium audit is planned.