Calibre gives you a complete picture of your website's performance through three complementary approaches: real-user data from Google’s Chrome User Experience Report (CrUX), your own Real User Monitoring (RUM), and controlled Synthetic testing. You can use any combination of these depending on your goals.
This guide walks you through setting up each one. If you have questions along the way, contact our friendly support team.
Step 1: Add your Sites to Calibre#
To start monitoring, add a Site by providing a name and URL, then assign it to a Team. You'll also choose settings for synthetic testing — a test location and schedule — which Calibre uses to run controlled performance tests. You can monitor unlimited sites and pages at no extra cost.
After creating a Site, Calibre will begin working for you in the background:
- Synthetic tests run three consecutive Snapshots to establish a reliable baseline. We'll email you when results are ready.
- CrUX data is gathered by spidering your site to discover your most important pages and matching them against Google’s CrUX dataset. Initial results are typically available within 30 minutes.
- Real User Monitoring can be enabled at any time by installing a lightweight JavaScript snippet — more on that in Step 3.
Once your Site is created, you can configure Test Profiles, add pages to monitor, and connect integrations like Slack and GitHub.
Step 2: Explore real-user data with CrUX#
Every Site you add to Calibre automatically gets a CrUX Dashboard. CrUX provides real-user performance data sourced from Google’s Chrome User Experience Report — the same data Google uses as a ranking signal in Search. There's no tracking script to install and it's included on all plans.
Your CrUX Dashboard shows Core Web Vitals and Web Vitals metrics, colour-coded so you can immediately see whether your site is passing or failing Google’s thresholds for Largest Contentful Paint, Cumulative Layout Shift, Interaction to Next Paint, and more.
Automatic page discovery#
Calibre automatically spiders your site and identifies your most important pages based on navigation structure and internal linking patterns. Pages with enough traffic to appear in the CrUX dataset are tracked and kept up to date as your site evolves — no manual URL management required.
You can view all discovered pages, their CWV scores, and their pass/fail status on the CrUX Pages Leaderboard. Navigate to Site → CrUX → Pages to see it.
Getting the most from CrUX#
- Filter by device type to compare Desktop, Tablet, and Phone experiences — performance differences across devices are often significant.
- Switch chart types between 75th percentile trends and experience distribution to understand whether most of your users are having a good experience.
- Click into individual pages from the Pages Leaderboard to see detailed metric histories.
CrUX data is a great starting point for identifying your biggest performance issues because it reflects what real users actually experience. However, sites must meet CrUX eligibility criteria — if your site or specific pages don’t have enough traffic, data may not be available.
Step 3: Set up Real User Monitoring#
For deeper, real-time insight into how your visitors experience your site, enable Real User Monitoring (RUM). Unlike CrUX, which aggregates data weekly from Chrome users, RUM collects performance data from every qualifying session on your site, across all browsers.
RUM is available on all Calibre plans, including the free trial.
What RUM gives you#
- A live dashboard showing current visitors, total sessions, audience locations, and the percentage of sessions with good Core Web Vitals.
- A Pages Leaderboard that ranks your pages by performance, with the ability to group pages into logical sets (like all blog posts or all product pages).
- Metric detail views with subpart breakdowns — for example, seeing exactly which phase of Largest Contentful Paint (TTFB, image load delay, render delay) is causing slowness.
- Audience reports showing how performance varies by country, device, browser, and more.
- Full control over sampling rates, geographic data collection, and data retention.
You can also track deployments in RUM, marking releases on your metric graphs so you can see how each deploy affects real-user experience.
Getting started with RUM#
To enable RUM, navigate to Site → Real User Monitoring → Settings, configure your allowed origins and sampling rate, then install the JavaScript snippet on your site. For detailed instructions, see Install & Configure RUM.
To learn more about RUM's reports and filtering capabilities, see Real User Monitoring.
Step 4: Configure Synthetic Monitoring#
Synthetic monitoring lets you test your pages under controlled, repeatable conditions. This is invaluable for catching regressions before they reach users, understanding performance under specific device and network scenarios, and running Lighthouse audits for performance, SEO, accessibility, and best practices.
Test Profiles#
Test Profiles define the conditions for each test — device emulation, network speed, authentication, and more. Calibre automatically creates two baseline profiles for every Site: PageSpeed Desktop and PageSpeed Mobile. You can customise these and create additional profiles to cover the range of conditions your users experience.
Viewing results#
- Pulse shows historical metric trends across Test Profiles, with deploy markers.
- Snapshot Overview gives you the full picture for a single test: metrics, render timeline, JavaScript long task analysis, asset breakdowns, and request details.
- Lighthouse audits surface opportunities for improvement across Performance, SEO, Best Practices, and Accessibility.
- Third Party tracking reveals how external scripts contribute to page weight and main thread time.
Budgets, alerts, and integrations#
Synthetic monitoring is where Calibre’s alerting and workflow integrations live:
- Performance Budgets — set thresholds on any metric and get notified when they're exceeded. Start with Largest Contentful Paint, Cumulative Layout Shift, and Total Blocking Time.
- Slack — receive budget alerts and snapshot summaries in a dedicated channel like #speed-metrics.
- Pull Request Reviews — see the performance impact of code changes before they ship (requires GitHub and a supported deployment method like Vercel, Netlify, or Heroku).
- Deploy tracking — mark releases on your metric graphs to correlate deployments with performance changes.
- Webhooks and Zapier — connect Calibre to your existing workflows.
Set up a dedicated Slack channel like #speed-metrics or #site-performance so your team can keep an eye on regressions and improvements.
For an in-depth walkthrough of synthetic monitoring setup and features, see our Synthetic monitoring documentation.
Step 5: Organise work with Teams#
Create Teams to organise people around the Sites they care about. You might divide Teams by project, business area, or client — whatever makes it easiest for people to focus on what's relevant to them.
Teams work together with user roles and permissions, so you can control who has access to what and avoid information overload.
Once you’re set up, continue exploring all of Calibre’s features or reach out to our support team for help refining your performance strategy.