Scan Comparison
Scan Comparison is the "diff view" for performance. Pick any two completed scans — usually before and after a publish — and see exactly which pages moved.
How to open it
Navigate to:
/sites/[siteId]/compare
Or click Compare on the site detail page.
The picker
Two dropdowns: Scan A (baseline) and Scan B (comparison). Each dropdown lists every completed scan for the site, newest first, with scan date and strategy.
Defaults to the two most recent completed scans — so opening the page without touching anything shows you "what changed since last scan." Good enough for most visits.
What you see
Summary cards
Site-level Performance, SEO, Accessibility, Best Practices, and Health. Each card shows A → B with a delta. Color-coded:
- Green — improved by more than 2 points
- Red — regressed by more than 2 points
- Gray — essentially unchanged
Per-page delta table
One row per page that appears in both scans. Columns:
| Column | Description |
|---|---|
| Page | URL path. |
| Strategy | Mobile / Desktop. |
| Performance Δ | Point delta, color-coded. |
| SEO Δ | Point delta. |
| Accessibility Δ | Point delta. |
| Best Practices Δ | Point delta. |
| LCP Δ | Millisecond delta. |
| CLS Δ | Ratio delta. |
| INP Δ | Millisecond delta. |
Sort by any column. Click a row to expand and see the full before/after numbers side by side.
Pages that only exist in one scan (new pages, or pages that were unpublished) are listed in a separate "Added" / "Removed" section at the bottom so you can see what changed structurally.
When to reach for it
- Post-deploy verification. Publish a change, run a scan, compare to the last pre-publish scan.
- Weekly reviews. Compare this week's Monday scan to last Monday's.
- Client deliverables. Paste the comparison URL into an email to show before/after in concrete numbers.
- Investigating a regression alert. Regression detection tells you something broke — Scan Comparison shows you which pages.
The page reads scanA and scanB from the URL, so bookmarks and pasted links restore the exact comparison. Useful for client threads — you can hand them a comparison they'll see even after three more scans run.
What's next
- Need one specific page across many scans instead? See Page Trends.
- Want this as structured data? Export both scans via Bulk Export and diff them yourself.