Performance belongs in design decisions
Design should consider asset count, media size, and when content appears. Avoid large libraries or animations when CSS and a little JavaScript can deliver the same experience.
Understand three aspects of experience
Core Web Vitals assess main content loading through LCP, interaction responsiveness through INP, and layout stability through CLS. Each reveals a different kind of problem, so reducing image size is not always the answer.
Supply images at suitable sizes
Choose image formats and dimensions for their display. Set width and height to reserve space early. Below-the-fold media can use lazy loading; do not delay the main image needed immediately.
Keep fonts and scripts efficient
Limit font families and variations, supply suitable files, and keep text visible during loading. Supporting scripts should not block core content or add unnecessary processing.
Distinguish lab tests from real-user data
Testing one device gives clues for improvement. Real-user data reflects varying networks, devices, and interactions. A new site may lack field data; do not treat a lab score as every visitor’s experience.
Make measurement a habit
Check the homepage and important templates after changes. Compare results under consistent conditions and prioritise issues affecting users. As content and features grow, performance needs ongoing care.
References & further reading
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