Browser compatibility is the practice of ensuring web applications render and function consistently across different browsers, versions, and devices. While modern browsers have converged significantly on standards support, rendering engines still differ (Chrome/Edge use Blink, Firefox uses Gecko, Safari uses WebKit), creating subtle inconsistencies in CSS layout, JavaScript APIs, and feature availability. The key is not universal perfection but strategic testing and graceful handling of edge cases—combining feature detection, polyfills when necessary, and transpilation for older environments. Think of compatibility work as an investment in reach: the broader your browser matrix, the larger your accessible audience, but each additional target browser multiplies testing complexity exponentially.

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