Practical guidance
Compare runs with consistent device and network profiles. LCP measures the largest visible element’s loading and CLS measures layout stability. Lab TBT helps identify blocking JavaScript but does not replace field INP.
Before using this tool
Define what you need from Website speed check and prepare the relevant input. When diagnosing a live service, record the test time and connection conditions so you can compare results after configuration changes. Check findings against the documentation for your software.
Tool availability
This is currently an information page. No working form, calculations or submission to diagnostic services is available yet. The interface and supported input formats will be documented when functionality is released.