Definition
The discipline of reducing page load time and render blocking so users receive usable content within roughly two seconds—critical for retention, conversion, and search ranking.
Why It Matters
Site performance is the ‘first impression’ of the digital age; it recognizes that in a world of sub-second attention spans, a slow-loading page is a failed product, regardless of how good the content is.
Core Concepts
- File Size Limits: Compress and optimize images; minify HTML, CSS, and JavaScript.
- HTTP Request Reduction: Fewer separate files means fewer round trips (sprites, concatenation).
- Script Loading: Defer or async non-critical JS so rendering is not blocked.
<!-- Loading scripts without blocking HTML parsing -->
<script async src="analytics.js"></script>
<script defer src="main-app-logic.js"></script>- Waterfall Charts: Browser Network tab visualizes each request’s timing and dependencies.
- Context Warning: Do not infer network speed from screen size alone.