PageSpeed

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, opportunities 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 First Input Delay Time (sec)
• CrUX First Input Delay 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 First Input Delay Time (sec)
• CrUX Origin First Input Delay 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
• Time to First Byte (ms)
• 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
• First Meaningful Paint Time (sec)
• First Meaningful Paint 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

Opportunities

• Eliminate Render-Blocking Resources Savings (ms)
• Defer Offscreen Images Savings (ms)
• Defer Offscreen Images Savings
• Efficiently Encode Images Savings (ms)
• Efficiently Encode Images Savings
• Properly Size Images Savings (ms)
• Properly Size Images Savings
• 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
• Serve Images in Next-Gen Formats Savings (ms)
• Serve Images in Next-Gen Formats Savings
• Enable Text Compression Savings (ms)
• Enable Text Compression Savings
• Preconnect to Required Origin Savings
• Server Response Times (TTFB) (ms)
• Server Response Times (TTFB) Category (ms)
• Multiple Redirects Savings (ms)
• Preload Key Requests Savings (ms)
• Use Video Format for Animated Images Savings (ms)
• Use Video Format for Animated Images Savings
• Total Image Optimization Savings (ms)
• Avoid Serving Legacy JavaScript to Modern Browser Savings

Diagnostics

• DOM Element Count
• JavaScript Execution Time (sec)
• JavaScript Execution Time Category
• Efficient Cache Policy Savings
• Minimize Main-Thread Work (sec)
• Minimize Main-Thread Work Category
• Text Remains Visible During Webfont Load
• Image Elements Do Not Have Explicit Width & Height
• Avoid Large Layout Shifts

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

Filters

This tab includes the following filters.

• Eliminate Render-Blocking Resources – This highlights all pages with resources that are blocking the first paint of the page, along with the potential savings.
• Properly Size Images – This highlights all pages with images that are not properly sized, along with the potential savings when they are resized appropriately.
• Defer Offscreen Images – This highlights all pages with images that are hidden or offscreen, along with the potential savings if they were lazy-loaded.
• Minify CSS – This highlights all pages with unminified CSS files, along with the potential savings when they are correctly minified.
• Minify JavaScript – This highlights all pages with unminified JavaScript files, along with the potential savings when they are correctly minified.
• Reduce Unused CSS – This highlights all pages with unused CSS, along with the potential savings when they are removed of unnecessary bytes.
• Reduce Unused JavaScript – This highlights all pages with unused JavaScript, along with the potential savings when they are removed of unnecessary bytes.
• Efficiently Encode Images – This highlights all pages with unoptimised images, along with the potential savings.
• Serve Images in Next-Gen Formats – This highlights all pages with images that are in older image formats, along with the potential savings.
• Enable Text Compression – This highlights all pages with text based resources that are not compressed, along with the potential savings.
• Preconnect to Required Origin – This highlights all pages with key requests that aren’t yet prioritizing fetch requests with link rel=preconnect, along with the potential savings.
• Reduce Server Response Times (TTFB) – This highlights all pages where the browser has had to wait for over 600ms for the server to respond to the main document request.
• Avoid Multiple Page Redirects – This highlights all pages which have resources that redirect, and the potential saving by using the direct URL.
• Preload Key Requests – This highlights all pages with resources that are third level of requests in your critical request chain as preload candidates.
• Use Video Format for Animated Images – This highlights all pages with animated GIFs, along with the potential savings of converting them into videos.
• Avoid Excessive DOM Size – This highlights all pages with a large DOM size over the recommended 1,500 total nodes.
• Reduce JavaScript Execution Time – This highlights all pages with average or slow JavaScript execution time.
• Serve Static Assets With An Efficient Cache Policy – This highlights all pages with resources that are not cached, along with the potential savings.
• Minimize Main-Thread Work – This highlights all pages with average or slow execution timing on the main thread.
• Ensure Text Remains Visible During Webfont Load – This highlights all pages with fonts that may flash or become invisible during page load.
• Image Elements Do Not Have Explicit Width & Height – This highlights all pages that have images without dimensions (width and height size attributes) specified in the HTML. This can be a big cause of poor CLS.
• Avoid Large Layout Shifts – This highlights all pages that have DOM elements contributing most to the CLS of the page and provides a contribution score of each to help prioritise.
• Avoid Serving Legacy JavaScript to Modern Browsers – This highlights all pages with legacy JavaScript. Polyfills and transforms enable legacy browsers to use new JavaScript features. However, many aren’t necessary for modern browsers. For your bundled JavaScript, adopt a modern script deployment strategy using module/nomodule feature detection to reduce the amount of code shipped to modern browsers, while retaining support for legacy browsers.

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.