The Performance metrics page shows the core Lighthouse performance timings Siteimp collected for one page.

This page is a focused page-level view. It does not try to explain the entire scan. It shows the performance evidence collected for the page you are currently reviewing.

Use it when you want to understand how quickly meaningful content appeared, how stable the page remained during load, and whether the page did blocking work on the main thread.

What this page is for

The Performance metrics page helps answer:

  • what performance score did Lighthouse assign to this page?
  • was the page audited in desktop or another Lighthouse mode?
  • how quickly did content appear?
  • when did the largest visible content appear?
  • how much main-thread blocking work happened?
  • did the layout shift during load?
  • are the page metrics available for this scan?

These metrics are evidence, not a full diagnosis by themselves. They help you decide where to look next.

Overview

The Overview section summarizes the two highest-level facts for the page.

Performance score shows the Lighthouse performance score for this page. Siteimp displays it as a whole-number score.

Mode shows the Lighthouse mode used for the audit, such as desktop.

The score is useful for orientation. The individual metrics below are usually more useful when deciding what needs to be fixed.

Metrics table

The Metrics table lists the page performance measurements collected for this scan.

Each row includes:

  • Metric, the name of the performance measurement
  • Value, the collected value
  • Unit, such as ms or score

Milliseconds measure time. Lower is generally better.

Score values are unitless measurements. For example, Cumulative Layout Shift is shown as a score rather than milliseconds.

Common metrics

First Contentful Paint

First Contentful Paint measures when the browser first rendered visible content.

A faster value usually means the page gives users feedback sooner.

Largest Contentful Paint

Largest Contentful Paint measures when the largest meaningful visible content appeared.

This is often one of the most important user-perceived load metrics because it approximates when the page’s main content became visible.

Total Blocking Time

Total Blocking Time measures how much main-thread work could delay user interaction.

A high value can mean JavaScript or other work is preventing the page from responding quickly.

Speed Index

Speed Index estimates how quickly the page visually filled in.

It is useful for understanding the overall visual loading experience.

Time to Interactive

Time to Interactive estimates when the page became reliably interactive.

A page can look loaded before it is actually ready to respond well. This metric helps expose that gap.

Cumulative Layout Shift

Cumulative Layout Shift measures how much the page layout moved unexpectedly during load.

Lower is better. Unexpected shifts can make pages feel unstable and can cause users to click the wrong thing.

How to use this page

Start with the performance score, then inspect the rows.

A practical workflow is:

  1. Check the Lighthouse mode.
  2. Review the performance score.
  3. Look for unusually high timing values.
  4. Check Cumulative Layout Shift for page stability.
  5. Compare this page to other pages in the same scan.
  6. Open the page in a browser if a metric looks surprising.
  7. Use the score as a starting point, not the whole story.

Performance work is rarely solved by one number. The table gives you clues about which part of the loading experience needs attention.

Why metrics may differ between scans

Performance metrics can change between scans.

They may be affected by:

  • machine load
  • network conditions
  • server response time
  • third-party scripts
  • image or font loading
  • cache state
  • Lighthouse mode
  • changes to page content

Use repeated scans to confirm patterns before treating one unusual result as permanent.

Metrics page not found

If Siteimp shows Metrics page not found, the route did not include a valid scan and page combination.

Return to the page results table and open Performance metrics from the page detail view.

Failed to load page metrics

If Siteimp shows Failed to load page metrics, the app could not load the performance metrics for this page.

Return to the page results view and try again. If the problem continues, contact technical support and include the scan number, page URL, and error text shown in the app.

Why this page may be empty

If Siteimp says No metrics are available for this page, the scan did not have page metrics available for this page.

That can happen when Lighthouse did not complete for the page, the page could not be fetched cleanly, or the scan ended before metrics were collected.