Browser support for module systems is an important consideration: 1) ES Modules are natively supported in modern browsers using <script type='module'>, 2) CommonJS is not natively supported in browsers and requires bundling or transpilation, 3) ES Modules work directly in browsers with proper MIME types and module script tags, 4) CommonJS was designed for server-side Node.js and doesn't have browser implementation, 5) ES Modules' browser support enables better development experiences with proper caching and loading optimizations, 6) Using CommonJS in browsers requires tools like Browserify or Webpack, 7) ES Modules' native browser support makes them the preferred choice for modern web development.