> ## Documentation Index > Fetch the complete documentation index at: https://docs.vortexiq.ai/llms.txt > Use this file to discover all available pages before exploring further. # Load Speed Over Time, Website Performance (PageSpeed + CrUX) > Load Speed Over Time for Website Performance (PageSpeed + CrUX) stores. Tracked live in Vortex IQ Nerve Centre. How to read it, why it matters, and how to ... **Metrics type:** [Supporting Metrics](/nerve-centre/overview#metrics-types-explained) • **Category:** [Website Performance](/nerve-centre/connectors#connectors-by-type) ## At a glance > **Largest Contentful Paint p75 over time**, daily or monthly time-series of mobile LCP measured from CrUX. **The drift-detection view** that surfaces gradual performance degradation (or improvement) the static [`crux_lcp_p75`](/nerve-centre/kpi-cards/website-performance/page-load-speed) snapshot can't show. **Critical for monitoring** because LCP drift often happens slowly (added third-party tags, image-quality drift on uploaded content, CDN config changes) and goes unnoticed until it crosses a threshold weeks later. | | | | ---------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | **What it counts** | Time-series of `largest_contentful_paint` p75 across the rolling 28-day CrUX window, sampled at the cadence Vortex IQ refreshes (daily by default; monthly snapshots for long-term comparison). The metric value at each timestamp reflects the trailing 28 days of real-user data. | | **Sample type** | **Field data** sourced from CrUX. Lab-data trend is captured via [`psi_score_trend`](/nerve-centre/kpi-cards/website-performance/performance-score-over-time) which tracks Lighthouse score over time. | | **Why trend matters more than snapshot** | A snapshot can show "LCP is 3,200ms today"; the trend shows "LCP was 2,400ms three months ago and has crept up 800ms". **Drift detection** is the value: gradual degradation often goes unnoticed in spot-checks but accumulates into ranking-impact territory. | | **Common drift patterns** | (1) **Slow up-drift** (50-100ms/month): typical pattern when third-party tags accumulate without explicit cleanup. (2) **Step regression** (300-1,000ms in a single week): typically a deploy or content upload that introduced a new render-blocker. (3) **Slow down-drift** (improvement): post-optimisation absorption over the 28-day rolling window. (4) **Cyclical** (peak season variations): high-traffic periods (BFCM, Prime Day) often show LCP degradation due to server load. | | **Reading the trend** | Look at: (a) **direction** (up = bad, down = good); (b) **slope** (slow = drift, steep = regression); (c) **inflection points** (when did it change? cross-reference with deploy log); (d) **band crossing** (when did it cross 2,500ms threshold?). | | **The 28-day rolling smoothing** | Each daily data point is a 28-day rolling p75. **Sharp regressions appear gradually** in the trend view because they're being averaged with 27 days of pre-regression data. A real-world LCP regression from 2,400ms to 4,200ms produces a gradual trend rise over 28 days, not an instant cliff. | | **Sample size threshold** | Each daily point requires sufficient real-user volume in the trailing 28 days. Low-traffic sites may have null trend values. | | **Currency** | n/a, time-series of milliseconds. | | **Time window** | `28D rolling × T` (current + historical). | | **Alert trigger** | `current value > 2,500ms` OR `7-day rolling delta > +500ms` (regression). | | **Sentiment key** | `psi_lcp` | | **Roles** | owner, marketing, 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, mobile LCP trend over 6 months ending Wednesday 15 May 26. | Month | LCP p75 (mobile) | Δ vs prior | Notes | | ---------------------------- | ---------------: | -------------------: | ------------------------------------------------------------ | | Nov 25 | 2,380ms | (baseline) | Healthy; in good band | | Dec 25 | 2,460ms | +80ms | Modest drift | | Jan 26 | 2,720ms | +260ms | Crossed into "needs improvement" band | | Feb 26 | 3,180ms | +460ms | New hero carousel deployed (heavier images) | | Mar 26 | 3,840ms | +660ms | Klaviyo + Tidio + Hotjar tags added in marketing-driven push | | Apr 26 | 4,420ms | +580ms | Holiday hero campaign (BFCM-prep) hero images | | **May 26** | **4,820ms** | **+400ms** | **Current state, "poor" band** | | **Cumulative drift Nov→May** | | **+2,440ms (+103%)** | **6-month silent regression** | What the trend is telling us: 1. **The site has more than doubled its LCP over 6 months without anyone noticing.** Each individual month-over-month change looked modest (80-660ms); cumulatively the LCP has gone from healthy good-band (2,380ms) to failing poor-band (4,820ms). **No single deploy was clearly catastrophic**; the drift is the story. 2. **Three distinct contributing events** can be identified from the inflection points: (a) Feb 26 hero carousel deploy (+460ms): a marketing-driven design refresh that added heavier hero imagery without performance review; (b) Mar 26 marketing-stack expansion (+660ms): three new third-party tags added in a single sprint to support a new email and chat strategy; (c) Apr 26 BFCM-prep campaign images (+580ms): heavy seasonal imagery uploaded without optimisation discipline. 3. **Each contributing event individually felt acceptable** to the team that made it. The hero carousel was visually stunning; the marketing stack expanded customer engagement; the BFCM imagery was on-brand. **None of the teams making changes saw the cumulative LCP impact** because nobody was watching the trend. 4. **The recovery path requires reversing each contribution thoughtfully.** Image format conversion + responsive variants for hero + product images recovers \~1,500-2,000ms. Third-party tag deferral + GTM audit recovers another 400-600ms. Aggressive caching + CDN tuning recovers another 200-400ms. **Cumulative recovery target: 4,820ms → 2,200-2,400ms over a focused 6-week optimisation cycle.** 5. **Future protection: trend monitoring as a guardrail.** **Set an alert at +200ms vs 30-day baseline** so the next 200ms drift is caught immediately and traced to its cause. Prevents the next 6-month cumulative regression. The Vortex Mind Pre-Launch Readiness report can fire alerts on this signal. 6. **The 28-day rolling window's effect on the trend curve** is visible in the smoothness. A real-world step regression (e.g. the Mar 26 marketing-stack add) appears as a gradual rise over 28 days rather than a vertical cliff. **For attribution work, look 7-14 days before the inflection** to find the actual regression event date. The diagnostic flow when this card flags amber/red: 1. **Identify the dominant trend direction.** Up over months = drift; sharp step = single regression event. 2. **Cross-reference inflection points with deploy log + content management activity.** Most regressions trace to a specific date. 3. **Decompose into component contributions.** Was it third-party? First-party? Content uploads? Each cause has a different fix. 4. **Plan recovery to undo each contribution.** Multi-week cycle typical for accumulated drift. Rapid-response playbook: | Time horizon | Action | | ------------- | ----------------------------------------------------------------- | | First 1 hour | Identify whether trend is drift (slow rise) or regression (step). | | First 4 hours | Cross-reference inflection points with deploy log. | | First 7 days | Begin recovery work (image optimisation typically first). | | First 30 days | Trend reflects optimisations as 28-day rolling window absorbs. | | Ongoing | Set alert for +200ms drift to prevent recurrence. | ## Sibling cards merchants should reference together | Card | Why merchants reach for it | | ---------------------------------------------------------------------------------------------------- | --------------------------------------------------- | | [`crux_lcp_p75`](/nerve-centre/kpi-cards/website-performance/page-load-speed) | Static snapshot; this card is the time-series view. | | [`crux_inp_trend`](/nerve-centre/kpi-cards/website-performance/responsiveness-over-time) | INP trend; pair for full CWV trend picture. | | [`crux_cls_trend`](/nerve-centre/kpi-cards/website-performance/layout-stability-over-time) | CLS trend. | | [`crux_pass_rate_trend`](/nerve-centre/kpi-cards/website-performance/speed-test-pass-rate-over-time) | All-three pass rate trend. | | [`psi_score_trend`](/nerve-centre/kpi-cards/website-performance/performance-score-over-time) | Lab Performance Score over time. | | [`crux_regression_timeline`](/nerve-centre/kpi-cards/website-performance/crux-regression-timeline) | Regression detection across all CWV. | | [`psi_biggest_regression`](/nerve-centre/kpi-cards/website-performance/biggest-regression) | Per-URL regression view. | | [`psi_image_optimisation`](/nerve-centre/kpi-cards/website-performance/image-optimisation) | Common LCP fix lever. | | [`psi_third_party_cost`](/nerve-centre/kpi-cards/website-performance/third-party-cost) | Third-party drift commonly causes LCP regression. | ## Reconciling against the vendor's own dashboard **Where to look:** * **[GSC → Core Web Vitals report](https://search.google.com/search-console)**, surfaces 90-day trend. * **[CrUX Dashboard via Looker Studio](https://lookerstudio.google.com/)**, Google's official CrUX explorer with deeper trend analysis. * **[CrUX BigQuery dataset](https://github.com/GoogleChrome/CrUX#crux-on-bigquery)**, monthly snapshots back to 2018 for long-term historical analysis. **Why the Vortex IQ trend may differ from external trend views:** | Reason | Direction | What to do | | ---------------------------------------------------------------------------------------------------------------- | --------------------- | -------------------------------------------------------------------------------- | | **Aggregation cadence.** Vortex IQ samples daily; CrUX BigQuery samples monthly. | Different granularity | Use Vortex IQ for short-term drift detection; BigQuery for long-term historical. | | **Window timing.** Vortex IQ refreshes daily; CrUX has 1-2 day lag. | Vortex IQ **lags** | Wait for next refresh. | | **Smoothing.** Each Vortex IQ data point is the 28-day rolling p75 at that timestamp; not a snapshot of the day. | Smoothed | Sharp regressions appear as gradual rises in the trend view. | **Cross-connector reconciliation:** primarily internal (with [`crux_lcp_p75`](/nerve-centre/kpi-cards/website-performance/page-load-speed), [`psi_score_trend`](/nerve-centre/kpi-cards/website-performance/performance-score-over-time)). **Quick rule for support tickets:** if a merchant says *"I deployed a fix yesterday but the trend hasn't moved"*, the 28-day rolling window means yesterday's fix is one day in a 28-day average. **Wait 7-14 days for partial movement; 28 days for full reflection**. ## Known limitations / merchant FAQs **My LCP has crept up 800ms over 6 months. Where do I start the recovery?** Cross-reference inflection points with deploy + content-management activity. Most cumulative drift traces to specific events (a deploy, a content upload, a third-party tag addition); identifying the events lets you reverse them. **Tools to use**: deploy log, GTM audit log, CMS image-upload log, theme version history. **My trend looks flat but my LCP is in the poor band. What do I do?** The site has a stable but bad LCP. **No drift means no recent regression**; the issue is structural rather than progressive. **Address structural issues**: image format conversion, render-blocking CSS, slow server response. The optimisation playbook is the same as for a recently-regressed site, just no need for inflection-point investigation. **My deploy fixed LCP but the trend hasn't moved. Why?** The 28-day rolling window. Each daily data point includes 27 days of pre-deploy data plus 1 day of post-deploy. **Wait 7 days** for partial movement (then \~25 percent of the window is post-deploy); **14 days** for substantial movement; **28 days** for full reflection. **Why is my trend so smooth when I know my deploys have spikes?** The 28-day rolling window smooths spikes. Sharp single-day regressions appear as gradual rises in the trend view. **For attribution work**, the inflection point in the trend lags the actual regression event by \~7-14 days; look earlier than the visible inflection. **Should I use trend or snapshot?** Both. **Snapshot** answers "where am I now"; **trend** answers "where am I going". Use snapshot for ranking-impact decisions today; use trend for drift detection and recovery planning. **Can Vortex IQ alert me when LCP starts drifting?** Yes; alert trigger `7-day rolling delta > +500ms` catches step regressions; `current value > 2,500ms` catches threshold crossings. Configure in Vortex IQ → Alerts. **Why does my trend show null for some recent days?** Insufficient CrUX data for those windows. Sites with low or fluctuating traffic occasionally drop below the 1,000-session threshold; the metric returns null for affected days. **Use lab data** ([`psi_lab_lcp`](/nerve-centre/kpi-cards/website-performance/lab-load-speed)) as the fallback for those gaps. **Can I export this trend to share with stakeholders?** The Vortex IQ dashboard supports CSV export; the underlying CrUX BigQuery dataset is also publicly queryable for long-form reporting. The Vortex Mind Pre-Launch Readiness report includes trend snapshots in its outputs. *** ### Tracked live in Vortex IQ Nerve Centre *Load Speed Over Time* is one of hundreds of KPI pulses Vortex IQ tracks across Website Performance (PageSpeed + CrUX) and 70+ other ecommerce connectors. Nerve Centre runs the detection layer; Vortex Mind investigates the cause when something moves; Ask Viq lets you interrogate any number in plain English. [Start for free](https://app.vortexiq.ai/login) or [book a demo](https://www.vortexiq.ai/contact-us) to see this metric running on your own data.