title: CSS: Duplicate Selectors vs. Duplicate Declarations
body: <p>Which CSS authoring technique do rendering engines process more efficiently:</p>
  
  <p>1) repeating the same style property/value pair in multiple selectors, or</p>
  
  <p>2) grouping shared style properties in a single selector</p>
  
  <p>Example 1: Duplicate font-size, but less rules</p>
  
  <pre><code>p {
  font-size: 1em;
  color: #000;
  }
  
  h1 {
  font-size: 1em;
  color: #fff;
  }
  </code></pre>
  
  <p>or Example 2: More rules but one font-size</p>
  
  <pre><code>p, h1 {
  font-size: 1em;
  }
  
  p {
  color: #000;
  }
  
  h1 {
  color: #fff;
  }
  </code></pre>