At a glance
Per-URL ranking of the slowest-loading pages by Largest Contentful Paint, sorted descending. The card surfaces individual URLs (not just templates), with their LCP value, traffic share, and the LCP element that’s responsible. The most actionable per-URL view in the website_performance set: instead of “your site is slow on average”, it gives you specific URLs ranked by impact, so optimisation effort concentrates on the right pages first. URLs with low LCP × high traffic share are the highest-leverage fixes; URLs with low LCP × low traffic are tail and can be deferred.
| What it counts | List of URLs from the audited site, each with: URL, mobile LCP value (lab), desktop LCP value, traffic share (from GA4 if connected, else equal-weighted), LCP element type (image, video, text, etc.), and recommended optimisation. Sorted by LCP descending. |
| Sample type | Lab data (per-URL Lighthouse audits). Field data per-URL is available in CrUX URL-level dataset for high-traffic URLs only. |
| Audit scope | Vortex IQ schedules per-URL audits for the merchant’s configured URL list (typically homepage + top product/category pages from the integration setup). Default depth: 30-50 URLs covering homepage, top-by-traffic product pages, top-by-traffic categories, and key checkout pages. |
| Why per-URL matters | Origin-level metrics average across URLs, hiding which specific pages are dragging the average. The same site can have a healthy homepage and a broken product detail page; origin-level shows “needs improvement” without indicating where to fix. Per-URL ranking surfaces the dragging pages directly. |
| Traffic-weighted decision making | The right optimisation priority is LCP × traffic share, not LCP alone. A URL with 8s LCP but 0.5 percent traffic share affects fewer customers than a URL with 4s LCP and 25 percent traffic share. The card surfaces both dimensions; the merchant decides priority. |
| Common patterns | (1) Homepage typically slowest by absolute LCP: heavy media. (2) Top-traffic PDPs second: hero product image LCP. (3) Top categories third: 12-image grid. (4) Tail PDPs and tail categories: variable, often inherit theme issues. |
| Currency | n/a, list with millisecond annotations. |
| Time window | T (current state from latest audit). Per-URL trends available via crux_lcp_trend when CrUX URL-level data is available. |
| Alert trigger | top URL > 4000ms LCP (any single URL in the poor band). |
| Sentiment key | null |
| Roles | owner, operations |
Calculation
Calculated automatically from your Website Performance (PageSpeed + CrUX) data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.Worked example
A UK-based BigCommerce fashion store, 30-URL audit, mobile, Wednesday 15 May 26.| Rank | URL | Mobile LCP | Traffic share | LCP element | LCP × traffic |
|---|---|---|---|---|---|
| 1 | /products/spring-floral-maxi-dress | 5,820ms | 8.4% | Hero JPEG (1.4MB) | 489 |
| 2 | / (homepage) | 4,820ms | 22.0% | Hero PNG carousel (slide 1, 2.8MB) | 1,060 |
| 3 | /collections/new-arrivals | 4,610ms | 12.0% | First product image in 12-image grid (380KB) | 553 |
| 4 | /products/leather-tote-bag | 4,480ms | 6.8% | Hero JPEG (1.2MB) | 305 |
| 5 | /products/gold-statement-earrings | 4,320ms | 5.2% | Hero JPEG (980KB) | 225 |
| 6 | /collections/sale | 4,180ms | 7.8% | First product image (340KB) | 326 |
| 7 | /products/silk-scarf-print | 3,940ms | 4.1% | Hero JPEG (920KB) | 162 |
| 8 | /collections/dresses | 3,820ms | 9.2% | First product image (320KB) | 351 |
| 9 | /products/casual-cotton-tshirt | 3,650ms | 3.8% | Hero JPEG (840KB) | 139 |
| 10 | /about | 3,420ms | 0.8% | Banner image (520KB) | 27 |
| … | (20 more URLs) |
- The homepage tops the LCP × traffic ranking despite not having the slowest LCP. Spring floral maxi dress page has 5,820ms LCP (slowest), but its 8.4 percent traffic share produces a lower commercial impact than the homepage’s 4,820ms × 22 percent = 1,060 weighted score. The homepage should be optimised first despite not being the absolute-slowest URL.
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Pattern: every page over 4 seconds has a hero image as the LCP element. The fix-pattern is uniform: image format conversion (WebP/AVIF), responsive variants via
srcset, preload directive on the LCP image, possibly lazy-loading downstream images. One coordinated optimisation cycle handles 6 of the top 10 URLs. - PDPs (product detail pages) cluster in the LCP 4,000-5,800ms range. The Stencil theme’s PDP template uses a single large hero image; 7 of the top-10 URLs are PDPs. The fix is structural to the PDP template rather than per-page; one template fix improves all 78 PDPs simultaneously.
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Collection pages cluster at 3,800-4,600ms LCP. The first image in the 12-image grid is the LCP element (it’s the largest above-the-fold element). Adding
loading="lazy"to images 5-12 plus image format conversion drops collection LCP by 800-1,200ms typically. - Tail pages (about, contact, terms, etc.) below rank 10 have low traffic share and slower LCP than ideal but lower priority. Defer until the high-traffic pages are fixed.
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Recommended optimisation sequence by LCP × traffic ranking:
- Week 1: Homepage hero carousel optimisation. Single biggest commercial impact.
- Week 2: PDP template hero image optimisation. Affects 78 PDPs simultaneously via template change.
- Week 3: Collection page first-image optimisation + lazy-load below-fold.
- Week 4+: Re-audit; address any URLs still in poor band; tail cleanup.
- Commercial impact estimation: Bringing the homepage and top-3 PDPs from 5-6 seconds to 2.5 seconds typically lifts mobile conversion rate 2-5 percent on those pages. For a brand with 30 percent of mobile traffic on homepage and 25 percent on PDPs at 2 percent baseline conversion at £42 AOV, a 3 percent conversion lift on those pages translates to £8,000-£12,000/month in incremental revenue.
- Sort by LCP × traffic. Don’t optimise the absolute-slowest URL if it has low traffic; commercial impact follows the weighted score.
- Identify the LCP element pattern. When the LCP element is the same type across many URLs (hero JPEG on PDPs), a template-level fix is more efficient than per-URL fixes.
- Confirm the fix on one representative URL first. Implement on one, audit, measure; only then propagate to similar URLs.
- Re-rank after each ship. Removing the homepage from the top usually reveals a different priority for the next round.
| Time horizon | Action |
|---|---|
| First 1 hour | Identify top 3 by LCP × traffic. |
| First 24 hours | Implement fix on the highest-leverage URL. |
| First 7 days | Field LCP movement on that URL (per-URL CrUX if available). |
| First 30 days | Cumulative ranking shift; second-priority URL becomes top. |
Sibling cards merchants should reference together
| Card | Why merchants reach for it |
|---|---|
crux_lcp_p75 | Origin-level LCP; this card decomposes by URL. |
psi_lcp_by_template | LCP by template type (homepage, PDP, collection); coarser grouping than per-URL. |
psi_worst_cls_urls | Same per-URL view for CLS. |
psi_worst_inp_urls | Same per-URL view for INP. |
psi_image_optimisation | Per-image opportunities; pairs with this card to identify which images on which URLs need work. |
psi_biggest_regression | URLs with biggest LCP regression vs prior period. |
psi_all_cwv_pass | Per-URL all-three CWV pass status. |
psi_perf_score_summary | Composite score; URLs with worst LCP often drag the composite. |
GA4 ga_pageviews_per_session | Traffic share input for the LCP × traffic weighting. |
Reconciling against the vendor’s own dashboard
Where to look:- PageSpeed Insights, paste each URL individually for per-URL LCP measurement.
- Google Search Console → Core Web Vitals, surfaces URL groups failing CWV; group-level rather than individual URL.
- CrUX URL-level dataset, for the highest-traffic URLs, CrUX provides per-URL p75 measurements.
| Reason | Direction | What to do |
|---|---|---|
| Run-to-run variance. Lighthouse LCP fluctuates ±10-20 percent between runs. | Either direction | Use 7-day rolling per-URL average. |
| URL set differences. Vortex IQ audits the configured URL list; PSI runs whatever URL is pasted. | Different scope | Confirm same URL for direct comparison. |
| Traffic share weighting. Vortex IQ weights by GA4 traffic share when GA4 is connected; PSI doesn’t weight at all. | Different ranking criterion | The weighted ranking is more commercially actionable. |
crux_lcp_p75, psi_image_optimisation, and traffic share data from GA4.
Quick rule for support tickets: if a merchant says “PSI says my homepage LCP is 3.2s but your card shows 4.8s”, the most common cause is run-to-run variance. Re-run PSI 3 times, average the results; should match Vortex IQ within 300-500ms.
Known limitations / merchant FAQs
My slowest URL has 0.5 percent traffic share. Should I still fix it? Probably not first. The LCP × traffic weighting concentrates effort where commercial impact is largest. Fix high-traffic URLs first; tail URLs often share the same root cause (template-level fix) and improve as a side effect of fixing high-traffic pages. Why does my homepage LCP differ between this card and the headline LCP card? The headlinecrux_lcp_p75 shows origin-level field data (real users, 28-day rolling); this card shows lab-measured per-URL data (synthetic single run). Lab and field can differ for many reasons (run-to-run variance, real-user device mix). Both are correct for their purpose: lab for engineering iteration, field for ranking truth.
Should I audit every URL on my site?
No. Vortex IQ defaults to ~30-50 representative URLs (homepage, top PDPs, top categories, key checkout pages). Auditing 1,000+ URLs adds API rate-limit pressure and rarely surfaces issues different from the representative set. Add specific URLs to the audit list if they’re high-traffic and not in the default set.
Some URLs in the list have no LCP element identified. Why?
A few possibilities. (1) The URL didn’t load successfully during the audit (404, 500, redirect to login). (2) The page has no above-the-fold visible element large enough to qualify (rare). (3) The audit timed out before the LCP element finished rendering. Verify the URL loads correctly in a fresh browser before treating the LCP value as valid.
Can Vortex IQ run audits on every PDP individually?
Technically yes; commercially marginal value. The PageSpeed API rate-limit (4 req/sec, 25k/day) caps practical audit volume. Recommended audit scope: top 30-50 URLs by traffic. The pattern across the top set typically reveals template-level issues that apply to the long tail.
Is the traffic share from GA4 or from BC’s analytics?
GA4 if connected; BC’s session count if GA4 is unavailable. GA4 is more accurate for true visitor behaviour because it tracks across sessions and devices; BC’s session count is closer to raw page-loads. The card uses whichever is available; the ranking is reasonable either way.