The comparison report puts two scans of the same URL side by side. This makes visible what actually changed between two points in time – not just in the score, but in individual metrics, issues and visually in the screenshot.
When a comparison is useful
A single scan shows what the page looked like at one particular moment. The comparison answers the real question:
- Did performance genuinely improve after the deployment?
- Which metrics changed, and which did not?
- Has the page become slower after a plugin update?
- Was yesterday's poor score an outlier or a trend?
How to open a comparison
There are two ways:
From the scan history: the history block on a scan report has an "Open comparison" button. It opens the comparison between the current scan and the nearest other scan.
From the domain view: the domain overview (/my-domains/{domain}) has the compare picker: you select any two scans of that domain from the dropdowns and click "Compare scans". This lets you put any two points in time next to each other – not just immediate predecessors.
What the comparison report shows
Score difference
At the top you see immediately whether scan A is better or worse than scan B – with the absolute difference and a colour-coded rating.
Metrics comparison
All the central metrics are shown side by side:
- TTFB, FCP, LCP, TBT, CLS
- Requests and data volume
- Sub-scores (Speed, Images, Caching, WordPress, Technical)
Changed values are highlighted so that you can see straight away where the differences are.
New and resolved issues
The comparison shows which issues are new in the current scan and which have been resolved compared with the reference scan. This is often more meaningful than the score difference on its own.
Screenshot comparison
If both scans captured a desktop or mobile screenshot, you can lay the pages next to each other visually:
- The Desktop and Mobile tabs switch between profiles
- Drag the slider from left to right to blend between before and after
- Quickly shows whether layout, content or visual structure has changed
The screenshot slider is no substitute for metrics, but it gives you an immediate sense of visible changes.
Mobile vs. desktop
If both scans measured mobile and desktop, the comparison shows the differences per profile separately. Especially with mobile anomalies (more requests, higher load times), this is often the decisive clue.
Comparison vs. baseline
A comparison is flexible: you pick any two scans. A baseline is a fixed reference point that is compared against automatically.
For spontaneous before/after checks, the direct comparison is simpler. For continuous monitoring and alert thresholds, a baseline is the better starting point.