Core Web Vitals (CWV)

Real-user Core Web Vitals for Drupal.

Captures LCP, CLS, INP, FCP, and TTFB from real visitor browsers using the standard web-vitals JS. Stores them in two tables: cwv_beacons for real-user data, cwv_probes for cron-driven synthetic observations. Renders correlation panels at /admin/reports/cwv that join each metric to backend signals.

What you can answer out of the box:

• Does Drupal's page cache hit rate predict LCP on this route?
• Are slow INP outliers concentrated on logged-in pages?
• Did the count of "poor" beacons shift after the deploy on Tuesday?
• Which routes have the worst p75 TTFB?

No third-party service. No JS calls to external endpoints. Data stays in your database.

Privacy and hardening. Capture is off after install. Sampling defaults to 0.1. Per-IP flood protection and a configurable table-size guard defend the endpoint. Three URL-storage policies (hash, path-only, full) cover the GDPR / CCPA exposure the site can tolerate. Outlier filtering is on by default for new installs and drops obvious non-RUM noise (backgrounded-tab artefacts, broken-page beacons) before storage. SECURITY.md and PERFORMANCE.md in the repo cover the full posture and sizing tables.

Built as a substrate. A frozen, security-advisory-covered collector contract with four shapes (synchronous, async-decoration, probe, panel-contribution) lets sibling modules add their own context fields and report panels via a single tagged service. Built-in collectors ship the Drupal cache state, render-tree size, backend cache hit/miss, database query count, OPcache and APCu runtime health, edge-cache state across the major CDN vendors, and upstream / CDN request-ID correlation.

Roadmap in ROADMAP.md. Contract design in docs/collector-contract.md.