Lighthouse

LighthouseLighthouse is an open-source diagnostic tool from Google that audits a page's performance, accessibility and other quality aspects in a simulated lab environment.Open glossary entry → is an analysis tool from Google that audits a page in a simulated lab environment and provides, among other things, a performance score and concrete improvement suggestions. It is integrated into the Chrome DevTools and PageSpeed Insights, among others.

Lighthouse produces lab dataLab data are produced in a simulated test environment with fixed device and network conditions. They help identify the technical causes of performance problems.Open glossary entry → and is therefore mainly suited to diagnosis: it reveals, for example, the LCPLargest Contentful Paint (LCP) measures when the largest visible content element in the viewport has loaded, representing the perceived loading speed.Open glossary entry → element, render-blocking resourcesRender-blocking resources are files such as CSS or JavaScript that the browser must load and process before it can render the page, thereby delaying rendering.Open glossary entry → or unused JavaScript. Using it correctly matters:

• Lighthouse is a diagnostic tool, not a goal in itself.
• A score of 100/100 is not always economically worthwhile.
• What matters is fixing real user problems on important pages.

Because Lighthouse measures in the lab while Google Search ConsoleGoogle Search Console (GSC) is a free Google tool that shows how a website performs in organic search, with data on impressions, clicks, click-through rate and average position, plus indexing and technical issues.Open glossary entry → uses real user dataField data are performance measurements based on real users and their actual devices and connections. They show whether a performance problem is genuinely relevant.Open glossary entry → from the Chrome UX Report, the values can differ significantly. Lighthouse helps with troubleshooting but does not replace field dataReal User Monitoring (RUM) captures performance and experience data from real users during their actual visit. It provides so-called field data from real-world usage.Open glossary entry →.