Calibre is a web performance monitoring platform that helps teams measure, track, and improve website speed. It combines three data sources — Real User Monitoring, Google’s Chrome User Experience Report, and scheduled Synthetic Testing — into a single platform with alerting, performance budgets, CI/CD integration, and reporting.
What problem Calibre solves#
Web performance directly affects user experience, search engine rankings, and conversion rates. Most teams struggle to monitor it effectively because the data they need is spread across multiple tools:
- Google’s PageSpeed Insights for one-off audits
- Chrome User Experience Report data locked behind BigQuery or API calls
- Lighthouse CLI for local testing
- Separate Real User Monitoring, or APM providers for field data
Calibre brings all of these together, giving teams a single place to understand how their websites perform for real users, how Google sees their site, and how individual pages score in controlled synthetic tests.
Three data sources#
Calibre draws on three complementary data sources.
- Real User Monitoring (RUM) collects Core Web Vitals from actual browser sessions via a lightweight, privacy-first script — no cookies, no personally identifiable information.
- The Chrome User Experience Report (CrUX) is the same dataset Google uses for search ranking signals, tracked automatically without BigQuery setup.
- Synthetic Testing runs scheduled Lighthouse-based tests from global locations with configurable devices and network conditions, providing consistent measurements unaffected by real user traffic variations.
See the Glossary for detailed definitions of each concept.
Who uses Calibre#
Calibre is used by product teams, front-end developers, SEOs, and agencies who need to understand and improve web performance. Teams at companies use Calibre to monitor their websites.
It is designed for anyone responsible for how fast a website loads and how well it performs for its users, whether that is an engineering team tracking Core Web Vitals, a product manager monitoring the impact of new features, or an SEO specialist ensuring pages meet Google’s page experience requirements.
How Calibre fits into development workflows#
Calibre is designed to make performance part of the development process, not an afterthought.
It integrates with GitHub for pull request performance reviews, comparing the performance of preview deployments against the live site.
Teams receive alerts through Slack and can connect to other tools via Zapier.
A command-line interface and Node.js API enable automation and custom integrations.
Deployment markers annotate performance charts so teams can correlate changes in speed with specific releases.
Performance budgets define acceptable thresholds for metrics and automatically alert teams when those thresholds are exceeded.
For a detailed comparison with other performance monitoring approaches, see How Calibre is Different.
Company context#
Calibre Analytics was founded in 2017 and is headquartered in Melbourne, Australia. The company is bootstrapped, profitable, and intentionally operates as a small, focused team. Calibre has been built as a remote-first company from the start, serving customers across more than 60 countries.