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  • Writer's pictureBrent D. Payne

Avoid excessive DOM depth

The analyzed URL has a DOM structure with a depth that exceeds the optimal limit of 32 levels.

Why is this important?

A shallow DOM benefits your website's performance in many ways:

  • Network and load efficiency: Smaller DOMs mean fewer data to transmit, leading to a faster loading time, particularly for the content at the top of your pages.

  • Rendering performance: A less complex DOM improves the speed of re-calculations for layout and style every time the page is interacted with or scripts are run.

  • Memory usage: Using broad selectors like document.querySelectorAll('li') on a large DOM can consume a great deal of memory, which might negatively affect users with limited resources.

What does the Optimization check?

This Optimization is activated when the maximum DOM depth on an internal URL exceeds 32 levels.

Examples that trigger this Optimization:

This Optimization would be set off by URLs containing elements that push the DOM's depth over the 32-level threshold, for instance:

<!-- Example HTML structure that is too deep (simplified) --><div>  <div>    <!-- ...more nested elements... -->      <div> <!-- Depth exceeds 32 --> </div>    <!-- ...more nested elements... -->  </div></div>

How do you resolve this issue?

A well-designed DOM structure:

  • Contains fewer than 1500 total elements.

  • Has no more than 32 nested elements in any single path.

  • Avoids any single parent elements from having over 60 direct child elements.

Create and destroy DOM elements in real-time depending on the need to conserve memory and prevent clutter. Consider the possibility of postponing the creation of certain DOM nodes until necessary, such as after a scroll or click event.

To improve your DOM structure, consider these points:

  • Are layout tables being nested within one another excessively?

  • Do you find yourself adding extra <div> tags just to solve layout issues?

  • Could there be a more appropriate and semantically clear way to structure your markup?

Further Reading



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