Comparing Scans

The Scan Comparison page lets you compare the metrics of a specific URL across two different scans. This is useful for verifying that a performance fix has had the expected impact.

How to reach it

From the Page Report, click Compare Scans.

What you’ll see

The comparison view shows both scans side-by-side with a delta indicator for each metric:

• Core Web Vitals — LCP, CLS, INP, FCP, TTFB with improvement/regression indicators
• Asset sizes — JS, CSS, images, total payload
• Accessibility — issue count change
• Security — header status changes
• DOM metrics — node count, depth changes
• CO₂ — emission change
• Performance score — overall and category grade comparison

Interpreting results

• Green delta — the metric improved between the two scans
• Red delta — the metric regressed between the two scans
• Neutral — no meaningful change

Choosing scans to compare

Select the two scans you want to compare from the dropdown menus at the top of the comparison page. You can compare any two reports for the same page URL.

Tip

Run a scan before and after a deployment to confirm whether your changes improved or accidentally regressed performance.