PageSpeed Monitoring
Daily Lighthouse performance scores for your store, tracked over time, across mobile and desktop.
Cassian™ runs daily performance tests on your store using industry-standard Lighthouse methodology and tracks the results over time. You get lab scores (simulated, controlled conditions), Core Web Vitals, and real-user field data when it's available for your domain. The 30-day trend chart makes it easy to see whether performance is improving after changes — or quietly degrading.
What's Measured
Lighthouse Lab Scores (0–100)
| Score | What it means |
|---|---|
| Performance | Overall page speed — how quickly your store loads and becomes usable |
| Accessibility | How usable your store is for visitors with disabilities or assistive technology |
| Best Practices | Security posture, HTTPS usage, and adherence to modern web standards |
| SEO | Technical SEO compliance — structured data, meta tags, crawlability |
Score Thresholds
| Range | Rating | Colour |
|---|---|---|
| 90–100 | Good | Green |
| 50–89 | Needs improvement | Amber |
| 0–49 | Poor | Red |
These thresholds match the standard used by Google's own tooling.
Core Web Vitals
| Metric | What it measures |
|---|---|
| LCP (Largest Contentful Paint) | How long until the main content element is visible — images, hero text |
| CLS (Cumulative Layout Shift) | How much the page visually shifts while loading — a source of frustrating mis-clicks |
| INP (Interaction to Next Paint) | How quickly the page responds when a visitor taps a button or link |
Core Web Vitals are a direct input to Google's search ranking algorithm. Low scores here can affect your organic traffic.
Field Data
When your domain has enough real-world visitor traffic, Cassian shows field data alongside the lab scores. Field data reflects actual user experience — it updates more slowly (28-day rolling window) but is more representative than lab simulation.
Field data is only available for domains with sufficient real-world traffic. Newer or lower-traffic stores will only see lab scores initially.
Mobile vs Desktop
Cassian runs separate tests for mobile and desktop, and you can toggle between them on the dashboard card.
Mobile scores are typically lower than desktop. This is normal and expected — the mobile test simulates a slower network and a mid-range device. Google uses mobile performance for search ranking, so the mobile score is the one worth prioritising.
When Tests Run
PageSpeed tests run daily at 7 AM UTC. The dashboard always shows the most recent result. The 30-day trend chart shows how each score has changed day by day.
If you make changes to your theme or apps and want to see updated scores sooner, you can trigger a manual scan from the dashboard. PageSpeed runs automatically as part of each scan.
How to Enable PageSpeed Monitoring
Go to Sites in the sidebar and select your store.
Click Setup.
Toggle PageSpeed Monitoring to ON.
The first test runs within 24 hours, or sooner if you trigger a manual scan.
PageSpeed monitoring is available on all plans. The underlying test data comes from a publicly available performance API — there's no additional cost for any tier.
Where to See PageSpeed Data
Main dashboard → PageSpeed card shows:
- Current Performance score (mobile or desktop, togglable)
- Score pill badges for all four categories: Performance, Accessibility, Best Practices, SEO
- Core Web Vitals pills: LCP, CLS, INP — colour-coded by threshold
- Field data section (when available)
Click the card to expand the full 30-day trend chart, with the ability to filter by score category and toggle mobile/desktop.
How PageSpeed Affects Your Cassian Score™
PageSpeed data feeds into the Technical Health category of your Cassian Score™. However, the Cassian Score™ uses a broader set of signals — not just Lighthouse numbers. A low Performance score will pull your Cassian Score™ down, but fixing it alongside other technical issues has a compounding effect.
Frequently Asked Questions
Why is my mobile Performance score 38 when my desktop score is 74? The mobile test simulates a slower 4G network and a mid-range Android device. Most Shopify themes perform noticeably worse under these conditions. This gap is common and not a sign that something is broken — it's an opportunity to optimise image sizes, reduce third-party app scripts, and enable lazy-loading.
My score dropped 20 points overnight. Nothing changed. Why? PageSpeed lab tests can vary based on what content was cached, what third-party scripts loaded at test time, and transient network conditions. Single-day dips are normal. The 30-day trend is a better signal than any individual score. If the drop persists across multiple days, investigate recent app installations or theme changes.
Does the PageSpeed score affect my Cassian Score™? Yes. PageSpeed results contribute to the Technical Health layer of your Cassian Score™. A consistently low Performance score will suppress your overall score.
What's the difference between lab data and field data? Lab data is a simulated test run by Cassian under controlled conditions — consistent and repeatable. Field data comes from real visitors using your store, aggregated over a 28-day window. Lab data responds immediately to changes; field data takes weeks to reflect improvements.
My store is new and I have no field data — should I worry? No. Field data only appears once your domain accumulates enough real-world visitor data. Lab scores are fully functional and useful for all stores from day one.
I improved my theme — will I see the score change today? PageSpeed runs daily at 7 AM UTC. If you want to see updated scores sooner, trigger a manual scan from the dashboard. The test will pick up your latest theme within the next run cycle.
Can I see which specific elements are hurting my Performance score? The PageSpeed card shows your overall score and Core Web Vitals. Specific element-level diagnostics (like "image X is 4MB and causing your LCP") are available in the Issues section, where Cassian's technical analysis flags heavyweight resources.
What happens to my PageSpeed history if I downgrade my plan? Your score history is retained. Monitoring will pause if you move to a plan that doesn't include PageSpeed, and resume if you re-enable it later.