PageSpeed

The PageSpeed tab includes data from PageSpeed Insights which uses Lighthouse for ‘lab data’ speed auditing, and is able to look up real-world data from the Chrome User Experience Report (CrUX, or ‘field data’).

To pull in PageSpeed data simply go to ‘Configuration > API Access > PageSpeed Insights’, insert a free PageSpeed API key, connect and run a crawl. Data will then start to be populated against crawled URLs.

Please read our PageSpeed Insights integration guide on how to set up a free API and configure the SEO Spider.

Columns & Metrics

The following speed metrics, insights and diagnostics data can be configured to be collected via the PageSpeed Insights API integration.

Overview Metrics

• Total Size Savings
• Total Time Savings
• Total Requests
• Total Page Size
• HTML Size
• HTML Count
• Image Size
• Image Count
• CSS Size
• CSS Count
• JavaScript Size
• JavaScript Count
• Font Size
• Font Count
• Media Size
• Media Count
• Other Size
• Other Count
• Third Party Size
• Third Party Count

CrUX Metrics (‘Field Data’ in PageSpeed Insights)

• Core Web Vitals Assessment
• CrUX First Contentful Paint Time (sec)
• CrUX First Contentful Paint Category
• CrUX Largest Contentful Paint Time (sec)
• CrUX Largest Contentful Paint Category
• CrUX Cumulative Layout Shift
• CrUX Cumulative Layout Shift Category
• CrUX Interaction to Next Paint (ms)
• CrUX Interaction to Next Paint Category
• CrUX Time to First Byte (ms)
• CrUX Time to First Byte Category
• CrUX Origin Core Web Vitals Assessment
• CrUX Origin First Contentful Paint Time (sec)
• CrUX Origin First Contentful Paint Category
• CrUX Origin Largest Contentful Paint Time (sec)
• CrUX Origin Largest Contentful Paint Category
• CrUX Origin Cumulative Layout Shift
• CrUX Origin Cumulative Layout Shift Category
• CrUX Origin Interaction to Next Paint (ms)
• CrUX Origin Interaction to Next Paint Category
• CrUX Origin Time to First Byte (ms)
• CrUX Origin Time to First Byte Category

Lighthouse Metrics (‘Lab Data’ in PageSpeed Insights)

• Performance Score
• First Contentful Paint Time (sec)
• First Contentful Paint Score
• Speed Index Time (sec)
• Speed Index Score
• Largest Contentful Paint Time (sec)
• Largest Contentful Paint Score
• Time to Interactive (sec)
• Time to Interactive Score
• Max Potential First Input Delay (ms)
• Max Potential First Input Delay Score
• Total Blocking Time (ms)
• Total Blocking Time Score
• Cumulative Layout Shift
• Cumulative Layout Shift Score

Insights

• Number of Redirects
• Server Responds Quickly
• Applies Text Compression
• LCP Request Discovery
• LCP Breakdown
• Render Blocking Requests Savings (ms)
• Preconnect Candiates Savings (ms)
• Maximum Critical Path Latency (ms)
• Use Efficient Cache Lifetime Savings
• Layout Shift Culprits
• DOM Size
• Improve Image Delivery Savings
• Forced Reflow Savings (ms)
• Legacy JavaScript Savings
• Duplicated JavaScript
• Font Display Savings (ms)
• 3rd Parties

Diagnostics

• Minify CSS Savings (ms)
• Minify CSS Savings
• Minify JavaScript Savings (ms)
• Minify JavaScript Savings
• Reduce Unused CSS Savings (ms)
• Reduce Unused CSS Savings
• Reduce Unused JavaScript Savings (ms)
• Reduce Unused JavaScript Savings
• JavaScript Execution Time (sec)
• JavaScript Execution Time Category
• Efficient Cache Policy Savings
• Minimize Main-Thread Work (sec)
• Minimize Main-Thread Work Category
• Network Payload Size
• User Timing Marks and Measures

You can read more about the definition of each metric, opportunity or diagnostic according to Lighthouse.

Filters

This tab includes the following filters.

• Document Request Latency – Pages with resources that redirect, have a slow server response, or do not apply text compression. These can all contribute to latency and reducing page speed.
• LCP Request Discovery – Pages with a Largest Contentful Paint (LCP) request discovery that can be optimised.
• Render Blocking Requests – Pages with resources that are blocking the first paint of the page, along with the potential savings.
• Network Dependency Tree – Pages with a lot of latency on the critical path, caused by long chains and large resource download sizes.
• Use Efficient Cache Lifetimes – Pages with resources that are not cached, along with the potential savings.
• Layout Shift Culprits – Pages that have layout shifts on DOM elements without any user interaction such as elements being added, removed, or their fonts changing as the page loads.
• Improve Image Delivery – Pages where the download time of images can be reduced, improving the perceived load time of the page and Largest Contentful Paint (LCP).
• Forced Reflow – Pages with a forced reflow which can result in slowing down rendering and user interactions.
• Legacy JavaScript – Pages with legacy JavaScript. Polyfills and transforms enable legacy browsers to use new JavaScript features. However, many aren’t necessary for modern browsers.
• Duplicated JavaScript – Pages with duplicate JavaScript libraries across different code bundles. Lighthouse detects duplicated code that would be quicker to load once.
• Avoid Enormous Network Payloads – Pages with large network payloads that can reduce page speed. Large network payloads cost users real money and are highly correlated with long load times.
• Minify CSS – Pages with unminified CSS files, along with the potential savings when they are correctly minified.
• Minify JavaScript – Pages with unminified JavaScript files, along with the potential savings when they are correctly minified.
• Reduce Unused CSS – Pages with unused CSS, along with the potential savings when they are removed of unnecessary bytes.
• Reduce Unused JavaScript – Pages with unused JavaScript, along with the potential savings when they are removed of unnecessary bytes.
• Reduce JavaScript Execution Time – Pages with average or slow JavaScript execution time.
• Minimize Main-Thread Work – Pages with average or slow execution timing on the main thread.
• Optimize DOM Size – Pages with a large DOM size with a large layout or style recalculation exceeding a duration of 40ms.
• Font Display – Pages with fonts that may flash or become invisible during page load.

Please read the Lighthouse performance audits guide for more definitions and explanations of each of the opportunities and diagnostics above.

The speed opportunities, source pages and resource URLs that have potential savings can be exported in bulk via the ‘Reports > PageSpeed’ menu.

The ‘CSS Coverage Summary’ report highlights how much of each CSS file is unused across a crawl, and the potential savings that could be made by removing unused code that is loading across the site.

The ‘JavaScript Coverage Summary’ report highlights how much of each JS file is unused across a crawl, and the potential savings that could be made by removing unused code that is loading across the site.

PageSpeed Insights API Status & Errors

The PSI Status column shows whether an API request for a URL has been a ‘success’ and shows data, or there has been an error and no data is displayed. An ‘error’ usually reflects the web interface, where you would see the same error and message.

The ‘PSI Error’ column displays the full message received from the PSI API to provide more information about the cause. Some errors are due to the Lighthouse audit itself failing, other errors can be due to the PSI API being unavailable when the request is made.

Please read our FAQ on PageSpeed Insights API Errors for more information.