Changelog

Use the new CrUX Metric Report to analyse Core Web Vitals metrics for your Sites in greater detail. The Metric Report provides a comprehensive view of all Chrome User Experience Report metrics. Now, you can:

• View up to 24 months of historical data
• See Largest Contentful Paint (LCP) subparts, which help you understand the timings that make up the metric and where you can make improvements
• Break down performance by device type (Desktop, Tablet, Mobile)
• List the top 5 slowest pages for each metric
• Check User Experience distribution accordingly to Core Web Vitals thresholds (Good, To Improve & Poor)
• Visualise Core Web Vitals thresholds directly on charts, and correlate your data to recommended values

Largest Contentful Paint Subparts

Chrome User Experience Report (CrUX) provides "subparts" for LCP. Subparts break down the Largest Contentful Paint metric into its components. This helps you understand what contributes to your LCP measurements, allowing you to optimise performance in a targeted way.

The new Metric Report is available for all Sites tracked in Calibre. You can access it from the CrUX Dashboard, or directly from the sidebar navigation.

At the moment, Google only provides subparts for LCP, but we expect to see subparts for other Core Web Vitals metrics in the future.

This past few weeks we have made a few notable design and usability improvements, including:

Refreshed sidebar navigation

Sidebar navigation has been updated with a focus to improve usability, accessibility and consistency. These changes include:

• You can now navigate to sub-sections when the sidebar is collapsed.
• Sidebar navigation collapses sections to reduce clutter and improve readability.
• Improved keyboard navigation and overall accessibility for screen readers and other assistive technologies.
• Improved visual contrast in Light and Dark mode.

Date range filter for CrUX Dashboard

You can now filter CrUX Dashboard by date range.

The default view displays 3 months of Core Web Vitals history. You can view up to 24 months (Requires Calibre monitoring for 24 months).

Sharable report filters

Now, all reports in Calibre use URL parameters for filtering, so you can link your teammates to a pre-filtered report, or save as bookmarks.

Our Test Agents are now using Chrome 134 and Lighthouse 12.5.1 to test your Sites. You can find details surrounding the 12.5.1 release in the official Lighthouse changelog.

Today we have introduced a new Test Profile option that allows you to block requests to specified hosts in your Synthetic monitoring tests.

Using host blocking, you can specify a given host e.g.: example.com or even wildcard subdomains (e.g.: *.example.com), and all matching requests will be blocked during the test run.

Prior to this update, there were two options for blocking requests in your tests:

• Third Party Blocking
• Adblocking, powered by uBlock Origin browser extension

Due to changes introduced by the infamous "Manifest V3" extensions changes in Chrome, the future of adblocking extensions in Chrome is unclear. We can no longer consider adblocking extensions as a viable solution for automated monitoring.

In order to provide reliable alternatives to block hosts, we have immediately deprecated Adblocking, and replaced it with Host Blocking.

In most cases, Third Party Blocking is the recommended mechanism for blocking requests, as it is powered by an ever-growing list of known third party services and the hostnames they use.

You can find the new Host Blocking option in Test Profile settings (Site → Test Profile → (Add or Edit Test Profile) → Host Blocking).

For more information, see our Test Profile configuration documentation.

Today we're announcing a brand new web performance resource, the Website Speed Leaderboard.

We’ve ranked the world’s best known websites by Core Web Vitals, collected from millions of real users from Google’s Chrome User Experience Report (CrUX) dataset.

In leaderboards, websites are ranked based on their combined performance for Core Web Vitals metrics: Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Interaction to Next Paint (INP).

Leaderboards are organised into groups, so you can compare direct competitors and see who will be on top of the podium each month.

Currently, the Website Speed Leaderboard includes over 500 websites across 10 different sectors, with more on the way.

We hope this resource helps you understand how your site stacks up against the competition, and provides a benchmark for your performance goals.

Explore the Website Speed Leaderboard and share your feedback with us.

Back in 2021, we launched a free tool to check if your site passes Core Web Vitals, designed to make it trivial for anyone to have a Core Web Vitals Dashboard.

Today, we are excited to introduce an all new Core Web Vitals Test Tool.

This tool gives you a Core Web Vitals Dashboard that includes a full 6 month history of performance data, including in-depth breakdowns like Largest Contentful Paint (LCP) "sub parts", which help you understand what causes delays to LCP elements.

Each metric displays labels that indicate if performance has degraded over time or if it's in a good state.

Using detailed audience breakdowns, you can better understand how users interact with your site, including the types of devices they use, network latency, and the frequency of page loads from cache.

Using Core Web Vitals test, you can:

• See if your site passes Google’s Core Web Vitals assessment.
• Check which metrics need improvement.
• View performance history and trends over time.
• Share reports instantly, just copy the URL.

Generate your free report here.

We’re excited to announce a new free website speed test tool. You can use it to measure and improve the performance of your website—it’s completely free and available to everyone.

Here is what you can do with it:

• See if your site passes Google’s Core Web Vitals assessment.
• Check how fast your page loads from different locations and devices.
• Quickly audit performance, accessibility, SEO, and best practices.
• View page load videos, screenshots, and request logs.
• Share test results with colleagues or co-workers, no sign-up required.

You can run Desktop or Mobile tests from 3 global locations: Sydney (Australia), Frankfurt (Germany) or North Virginia (USA).

Each free report is available for 30 days and includes a sharable URL, making it easy to send to co-workers, clients, or a perf-buddy.

Every speed report features:

• Performance metrics from a synthetic Google Chrome browser session testing your page.
• Lighthouse audits to help you check-off low-hanging Performance, SEO, Best Practices improvements.
• Third Party report highlighting how third-party scripts and embeds impact page performance.
• Chrome User Experience Report Dashboard, including Core Web Vitals metrics, collected by Google for search ranking assessment (your site needs to meet Google’s collection criteria).

We hope you enjoy using this new tool and can’t wait to see your performance improvements out in the wild. Happy optimising!

Run your first test now: Website Speed Test

Our Test Agents are now using Chrome 131 and Lighthouse 12.3.0 to test your Sites. You can find details surrounding the 12.3.0 release in the official Lighthouse changelog.

As part of this update, Lighthouse 12.3.0 includes a reduction in CPU throttling (introduced in Lighthouse 12.2.3) that affects Calibre’s PageSpeed Mobile Test Profile preset.

PageSpeed Mobile’s CPU throttling multiplier has been lowered from 1.5 to 1.2, which results in lower Total Blocking Time (TBT) measurements, higher Performance score and faster overall main thread activity.

It is expected that you will observe an improvement in performance metrics for PageSpeed Mobile following this change.

The CPU throttling update was made by the Lighthouse team to better reflect real-world device performance.