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Critical CSS History

The Critical CSS History tab lets you track past CSS extractions, compare sizes, and revert to previous versions. This is crucial for catching CSS regressions after deployments.

schedule3 min readupdateUpdated Mar 9, 2026

Critical CSS History

The Critical CSS History tab provides a valuable record of all past critical CSS extractions performed by PerfBee. This feature allows you to track changes, identify potential issues, and easily revert to previous versions of your critical CSS.

What the History Tab Shows

Within the Critical CSS History, you'll find a detailed log of each extraction, including the following information:

  • Date: The exact date and time the extraction was performed.
  • URL: The URL of the page where the critical CSS was extracted.
  • CSS Size (bytes): The size of the extracted critical CSS file in bytes.
  • Similarity Score: A measure of how similar the current critical CSS is to the previous extraction.
  • Preset Used: Shows which preset was used for the extraction (e.g., mobile or desktop)

The history is paginated, displaying 20 entries per page, and you can easily search and filter by URL.

How to Use the Critical CSS History

Follow these steps to access and utilize the Critical CSS History:

  1. Navigate to the PerfBee Dashboard and log in.
  2. Go to the Critical CSS tab.
  3. Click on the History sub-tab.
  4. Review the extraction history.
  5. Use the search bar to filter by URL.
  6. To view the extracted CSS, click on any entry. You'll then be able to copy or re-download the CSS file.

Tracking CSS Size Changes

Monitoring the CSS size over time is crucial. Significant increases in size can negatively impact page load times. By reviewing the history, you can easily track these changes and identify when a design change or update has led to an increase in CSS bloat.

Catching Regressions

The Critical CSS History is invaluable for catching regressions after deployments. If you notice a drop in the similarity score or an increase in CSS size after a website update, you can quickly revert to a known-good critical CSS version from a previous extraction. This ensures a consistent and optimized user experience.

The ability to compare past extractions and re-download CSS files gives you a powerful toolset for maintaining optimal web performance.

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