How to Identify Dead Code on a Web Page Using Developer Tools in Google Chrome

DevTools for SEO

Identifying and removing dead code on a web page is an essential part of website optimization. Dead code refers to portions of the code that are no longer used or do not affect the functionality of the web page. Removing such code offers several benefits:

  • Improved Performance: Reducing the amount of code decreases page load times and improves website responsiveness.
  • Reduced Server Load: Fewer data transfers reduce the load on servers and networks, which is particularly important for high-traffic websites.
  • Enhanced Security: Dead code might contain outdated or vulnerable sections, and removing them improves overall site security.
  • Simplified Maintenance and Development: Clean, up-to-date code is easier to maintain and develop, reducing development costs.

Google Chrome’s DevTools can help us detect dead code.

Step 1: Open Developer Tools

  1. Open Google Chrome.
  2. Navigate to the site you want to analyze.
  3. Press Ctrl+Shift+I (Windows/Linux) or Cmd+Option+I (Mac) to open Developer Tools. Alternatively, right-click on the page and select Inspect.
Select "More tools" then "Coverage"

Step 2: Use the “Coverage” Panel

  1. Go to the Coverage tab in Developer Tools. If you don’t see it:
    • Open the three-dot menu in the top-right corner of the Developer Tools window.
    • Select More tools and then Coverage.
  2. Click the Record button in the Coverage panel.
Click the "Record" button.

Step 3: Reload the Page

  1. Reload the page by pressing F5 or Ctrl+R.
  2. The Coverage tool will track which parts of the code are loaded and used.
  3. Wait until the page fully loads and all scripts have finished executing.

Step 4: Analyze the Results

  1. In the Coverage table, you will see a list of files along with the percentage of code used.
  2. If a file shows a low percentage of usage, this could indicate that some of the code in that file is “dead.”

Step 5: Identify Unused CSS

  1. On the Elements tab, highlight elements on the page.
  2. In the right panel, under the Styles tab, you can see the CSS applied to those elements.
  3. If a CSS rule is not applied to any elements on the page, it may indicate dead code.
Searching for Dead CSS Code

Step 6: Test and Remove Dead Code

  1. Highlight elements on the Elements tab.
  2. In the right-hand Styles panel, check the CSS applied to the elements.
  3. If a CSS rule is not applied to any elements, it could be considered dead code.

Removing dead code can significantly improve your site’s loading speed in several ways:

  1. Reducing the Total Data Volume: Less code means fewer data to load.
  2. Decreasing Render Time: Less CSS and JavaScript leads to faster processing and rendering of the page.
  3. Minimizing HTTP Requests: Removing unused files reduces the number of HTTP requests.

These improvements collectively can greatly enhance site performance and improve the user experience.

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