Separate server and browser
Compare the time to the first byte and the moment the main content appears. Slow HTML requires checking PHP, database, external requests and hosting. If HTML is fast but the screen is blank for a long time, explore images, fonts, styles, and JavaScript. Repeat the test under the same conditions.
Continue with: Core Web Vitals: understand LCP, INP and CLS.
Reduce page load
Check image sizes for display, number of third-party widgets, and plugin resources that are not needed on this page. Do not postpone the main image without analysis: lazy loading for it can worsen the appearance of the main content. Check the change on a copy and record its individual effect.
Continue with: E-commerce caching: keep customer data private.
Check cache exceptions
The shopping cart, checkout, personal account and personal responses should not enter the shared cache. Check the form after long downtime, user login and two independent browsers. After optimization, evaluate both speed and correctness of functions; supplement the laboratory test result with field data, if available.
Do fewer plugins always mean a faster site?
No. Their requests and resources are important. One heavy component can have a stronger effect than several simple ones, so decisions are made based on measurements.