wp-performance/references/measurement.md

Measurement (profiling vs benchmarking)

Backend-only measurement options:

• WP-CLI profiling (wp profile): best for pinpointing slow hooks/stages without a browser.
• WP-CLI doctor (wp doctor): best for quick diagnostics (autoload bloat, debug constants, updates).
• Query Monitor via REST: use authenticated REST requests and inspect x-qm-* headers / qm envelope data.
• Server-Timing (Performance Lab): inspect Server-Timing headers via curl -I (when enabled).
• APM/profilers: New Relic, Datadog, Blackfire, Tideways, XHProf/Xdebug (requires server support).

Best practices:

• Always capture a baseline first.
• Keep the test scenario fixed (same URL/route, same user state, same data).
• Prefer multiple samples and medians over single runs.

References:

• Measuring performance handbook: https://make.wordpress.org/performance/handbook/measuring-performance/
• Benchmarking with Server-Timing: https://make.wordpress.org/performance/handbook/measuring-performance/benchmarking-server-timing/