Calibre

Calibre helps web developers, SEO teams, agencies, and product teams find and prevent website performance problems. It combines data from real visitors, Google’s Chrome User Experience Report, and scheduled tests under controlled device and network conditions, so teams can compare real-world experience with repeatable results. Dashboards track page speed, Core Web Vitals, and performance trends across sites and pages. Teams can set performance budgets and receive alerts when metrics cross their thresholds. Synthetic tests include Lighthouse audits for performance, SEO, accessibility, and best practices, plus details such as page render timelines and third-party script impact. GitHub pull request reports help developers check how code changes affect performance before release; Slack notifications, deployment markers, a command-line interface, and a Node.js API support team workflows and automation.

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