OBS Browser Source CSS: The Complete Guide

Modern streaming overlays are just web pages. That means every animation, layout tweak, and responsive adjustment you want is powered by CSS. In this guide you'll build a complete OBS overlay system that stays performant on air.

Why Browser Source CSS Matters

• Consistency across StreamElements, Streamlabs, or self-hosted overlays
• Brand control with custom fonts, gradients, and timing curves
• Performance without relying on heavy animation libraries

Overlay Architecture

<div class="overlay">
  <section class="alerts"></section>
  <aside class="event-list"></aside>
  <footer class="status-bar"></footer>
</div>

.overlay {
  display: grid;
  grid-template-columns: 2fr 1fr;
  grid-template-rows: auto 120px;
  gap: clamp(16px, 2vw, 32px);
  width: 1920px;
  height: 1080px;
  padding: 48px;
  background: radial-gradient(circle at top left, rgba(255, 105, 180, 0.3), transparent 60%);
}

Animation System

Use transform and opacity for GPU-friendly updates:

.alert {
  animation: slide-in 600ms cubic-bezier(0.22, 1, 0.36, 1);
}

@keyframes slide-in {
  from {
    transform: translateY(40px) scale(0.98);
    opacity: 0;
  }
  to {
    transform: translateY(0) scale(1);
    opacity: 1;
  }
}

Deploying to OBS

• Host assets on Netlify or GitHub Pages
• Use a single CSS bundle (inline critical styles for speed)
• Set the browser source FPS to 60 for smooth animation

Performance Checklist

• will-change: transform on frequently animated elements
• Avoid heavy box-shadows; prefer drop-shadow() filter
• Use prefers-reduced-motion to respect accessibility

Ready to ship? Package the overlay as a reusable template and link it in your stream commands. Your viewers will notice the polish immediately.