Stop Fighting Browsers: Build Once, Run Everywhere

You've been there. Your site looks perfect in Chrome, breaks spectacularly in Safari, and somehow makes IE cry. While other developers spend their weekends debugging browser quirks, you could be shipping features that work consistently across every browser your users actually use.

The Cross-Browser Development Problem

Modern web applications need to work flawlessly across browsers spanning a decade of evolution. Your users don't care that Safari handles flex gaps differently or that IE 11 doesn't support CSS Grid. They expect your application to work, period.

Here's what kills developer productivity in cross-browser development:

Hidden Compatibility Bombs: Features that work perfectly in your development browser but fail silently in production
Debugging Browser-Specific Issues: Spending hours tracking down why your layout breaks in Safari 14
Manual Testing Overhead: Constantly switching between browsers to verify every change
Inconsistent Styling: Fighting subtle rendering differences that make your design look unprofessional
Performance Variations: Code that's fast in Chrome but crawls in older browsers

Your Cross-Browser Compatibility Solution

These Cursor Rules transform your development workflow into a compatibility-first approach. Instead of discovering browser issues during QA, you prevent them during development with automated compatibility checks, standardized patterns, and battle-tested fallbacks.

You'll write code that works consistently from IE 11 to the latest Chrome, with built-in performance optimization and accessibility compliance.

Key Developer Benefits

Eliminate Browser Debugging Sessions Stop spending hours in Safari's Web Inspector trying to figure out why your flex layout collapsed. These rules provide proven fallback patterns for every major browser compatibility issue.

Ship Faster with Confidence Your code works across browsers the first time because compatibility is built into every pattern. No more "works on my machine" moments during deployment.

Automated Compatibility Validation Every component includes feature detection and progressive enhancement patterns. Your CI pipeline catches compatibility issues before they reach production.

Performance by Default Bundle splitting, lazy loading, and optimized asset delivery are built into the workflow. Your applications load fast on every browser and device.

Real Developer Workflows

Before: Manual Cross-Browser Development

// This breaks in Safari ≤14
.container {
  display: flex;
  gap: 1rem;
}

// Discover the issue during manual testing
// Spend 2 hours debugging flex gap support
// Implement hacky margin-based workaround

After: Compatibility-First Development

/* Built-in fallback pattern */
.container {
  display: flex;
  gap: 1rem;
}
@supports not (gap: 1rem) {
  .container { margin: -0.5rem; }
  .container > * { margin: 0.5rem; }
}

Feature Detection Over Browser Sniffing

// Wrong approach - fragile and unreliable
if (navigator.userAgent.includes('Safari')) {
  // Brittle browser-specific code
}

// Cursor Rules approach - robust feature detection
if ('serviceWorker' in navigator) {
  navigator.serviceWorker.register('/sw.js');
}

Safe Storage Handling

// Handles Safari private mode and quota exceeded
export const safeSet = (key: string, value: string) => {
  try { 
    localStorage.setItem(key, value); 
  } catch { 
    // Fallback: in-memory storage
    memoryStore.set(key, value);
  }
};

Responsive Images with Format Optimization

<picture>
  <source type="image/webp" srcset="hero.webp" />
  <source type="image/jpeg" srcset="hero.jpg" />
  <img src="hero.jpg" alt="Hero image" loading="lazy" />
</picture>

Implementation Guide

1. Set Up Your Compatibility Foundation

# Install essential compatibility tools
npm install --save-dev @babel/core @babel/preset-env
npm install normalize.css modernizr
npm install --save-dev playwright @playwright/test

2. Configure Your Browserslist

// package.json
{
  "browserslist": [
    "> 1%",
    "last 2 versions",
    "ie >= 11"
  ]
}

3. Add These Cursor Rules to Your Project

Copy the complete ruleset into your .cursorrules file. The rules include:

HTML5 Semantic Structure: Proper DOCTYPE, meta tags, and sectioning elements
CSS Compatibility Patterns: Mobile-first media queries, flexbox/grid fallbacks, custom property fallbacks
JavaScript Feature Detection: Safe API usage with polyfill integration
React Best Practices: Functional components with error boundaries
Testing Integration: Playwright E2E tests across browser engines
Performance Optimization: Bundle splitting, lazy loading, responsive images

4. Initialize Your Development Workflow

# Validate HTML during CI
npm run validate-html

# Test across browsers
npx playwright test

# Update browser database
npx browserslist --update-db

Expected Results & Impact

Development Speed: Reduce browser debugging time by 80%. Write compatibility code once instead of fixing issues across multiple browsers.

Code Quality: Every component includes proper fallbacks and feature detection. Your codebase becomes inherently more robust.

User Experience: Consistent performance and appearance across all supported browsers. Eliminate the "browser lottery" for your users.

Team Productivity: New developers can immediately write cross-browser compatible code using established patterns. No more compatibility knowledge silos.

Deployment Confidence: Automated testing across browser engines catches issues before production. Ship knowing your code works everywhere.

Performance Gains: Built-in optimization patterns (lazy loading, bundle splitting, responsive images) improve Core Web Vitals across all browsers.

These rules don't just solve cross-browser compatibility—they make it invisible. You'll write once and deploy everywhere, spending your time building features instead of debugging browser quirks.

Your users get a consistent, fast experience regardless of their browser choice. Your team gets predictable development velocity without compatibility surprises.

Ready to stop fighting browsers and start shipping? Add these rules to your project and watch your cross-browser development workflow transform from painful to automatic.

Cross-Browser Compatibility Ruleset