Topic

Rendering Performance & Optimization

RAIL goals, avoiding layout thrash, requestIdleCallback, preloading, and profiling paint/composite costs.

performancerailprofiling

HTML

sample

<div class="perf-card">Profile me</div>

CSS

sample

.perf-card { will-change: transform; transform: translateZ(0); }

JavaScript

sample

requestIdleCallback(() => console.log('Do background work here'))

Visualizer

Performance

RAIL and layout thrash simulator.

Visualizer

Rendering Performance

Keep frames under 16ms. Avoid layout thrash and defer heavy work.

live

Controls

Layout invalidations: 0

Visualization

FPS

RAIL: aim for 60fps; offload to workers.

Use requestIdleCallback for background work and postMessage to workers to keep the main thread free for rendering.

Why this matters

Connect the dots between specs (HTML, CSS, WebIDL) and engine behaviors (parser, layout, GPU). Use the sandbox to reproduce each step with your own snippets.