> ## 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. # Worst INP URLs, Website Performance (PageSpeed + CrUX) > Worst INP URLs for Website Performance (PageSpeed + CrUX) stores. Tracked live in Vortex IQ Nerve Centre. How to read it, why it matters, and how to act on... **Metrics type:** [Supporting Metrics](/nerve-centre/overview#metrics-types-explained) • **Category:** [Website Performance](/nerve-centre/connectors#connectors-by-type) ## At a glance > **Per-URL ranking of pages with the worst Interaction to Next Paint**, sorted descending. Surfaces individual URLs with their INP value, traffic share, and the dominant slow interaction (filter widget, sort dropdown, cart-drawer mount, etc.). **Completes the per-URL CWV trio** alongside [`psi_slowest_lcp_urls`](/nerve-centre/kpi-cards/website-performance/slowest-lcp-urls) and [`psi_worst_cls_urls`](/nerve-centre/kpi-cards/website-performance/worst-cls-urls). INP is the most JavaScript-driven of the three CWVs, so per-URL ranking surfaces interactive widgets that need engineering attention. | | | | ------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **What it counts** | List of audited URLs with their p75 INP value, traffic share, the worst interaction type captured during audit (or via field-data CrUX URL-level), and recommended fix. Sorted descending by INP. | | **Sample type** | **Mixed**: Lab Total Blocking Time (lab approximation of INP) for synthetic measurement, plus field INP from CrUX URL-level dataset where available. | | **Why per-URL matters for INP** | INP is interaction-driven; specific widgets on specific URLs fail it. Collection pages with filter widgets fail differently than PDPs with cart-drawer mounts. Per-URL ranking lets the merchant target specific widget refactors rather than treating INP as site-wide. | | **INP × traffic ranking** | Same logic as LCP and CLS cards: commercial impact = INP × traffic share. The card surfaces both dimensions. | | **Common dominant slow interactions** | (1) **Collection page**: filter checkbox click → faceted-search re-fetch + grid re-render. (2) **PDP**: "Add to cart" button → cart-drawer mount + analytics fire. (3) **Currency switcher**: page-wide price recalculation. (4) **Search overlay**: modal mount + product-search fetch. (5) **Sort dropdown**: change handler + grid re-render. (6) **Mobile menu**: drawer animation + JS state management. | | **Currency** | n/a, list with millisecond annotations. | | **Time window** | `T` (current state) for lab; `28D` for field measurements where available. | | **Alert trigger** | `top URL > 500ms INP` (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 US-based BigCommerce home goods store, 30-URL audit, mobile, Wednesday 15 May 26. | Rank | URL | p75 INP | Traffic share | Dominant slow interaction | INP × traffic | | ---: | ------------------------------ | ------: | ------------: | ----------------------------------------------------- | ------------: | | 1 | `/collections/lighting` | 720ms | 8.4% | Filter checkbox click (612ms) + sort dropdown (484ms) | 60.5 | | 2 | `/collections/furniture` | 680ms | 6.8% | Same filter widget pattern | 46.2 | | 3 | `/collections/all-products` | 612ms | 5.4% | Same filter widget pattern | 33.0 | | 4 | `/` (homepage) | 380ms | 22.0% | Currency switcher (720ms when used) | **83.6** | | 5 | `/collections/sale` | 540ms | 7.8% | Filter widget | 42.1 | | 6 | `/products/dining-table-large` | 420ms | 4.2% | Cart-drawer mount (cart-add interaction) | 17.6 | | 7 | `/collections/decor` | 480ms | 5.6% | Filter widget | 26.9 | | 8 | `/products/floor-lamp-modern` | 380ms | 3.8% | Cart-drawer mount | 14.4 | | 9 | `/search` | 460ms | 2.4% | Search-result render after type | 11.0 | | 10 | `/cart` | 220ms | 12.0% | Quantity update interaction | 26.4 | What the per-URL view is telling us: 1. **The homepage at INP 380ms ranks #4 by absolute but #1 by INP × traffic** (83.6 weighted score). Despite faster absolute INP than collection pages, the 22 percent traffic share dominates. The currency switcher is the slow interaction, page-wide price recalculation triggered when users switch from USD to GBP/EUR/CAD. **The homepage currency switcher is the highest-leverage INP fix.** 2. **Collection pages cluster at INP 480-720ms with the same dominant interaction**: the filter checkbox click. The faceted-search filter widget re-fetches and re-renders the product grid synchronously. **One template-level fix** (debounce + virtualise + defer analytics) improves all 12 collection pages simultaneously. Estimated post-fix: collection p75 INP drops to 200-280ms. 3. **PDPs (ranks 6, 8) have INP 380-420ms** with cart-drawer mount as the dominant interaction. The drawer mount triggers a JS-heavy component that causes a long task before paint. **Refactor cart-drawer to use CSS-driven slide animation with progressive enhancement**; estimated post-fix: PDP p75 INP drops to 150-200ms. 4. **The cart page at INP 220ms is healthy** but high-traffic (12 percent share), making it #4 by INP × traffic ranking. Don't optimise; monitor for regression. 5. **Search page (rank 9) has INP 460ms**, search-result rendering is the slow interaction. Lower priority due to low traffic share but worth a refactor when bandwidth allows. 6. **The recommended fix sequence by INP × traffic**: * **Week 1**: Homepage currency switcher refactor. Single biggest weighted impact. * **Week 2**: Collection page filter widget refactor. Affects 12 pages simultaneously. * **Week 3**: PDP cart-drawer mount refactor. Affects 78 PDPs simultaneously. * **Week 4**: Search-result rendering. Lower-priority polish. 7. **Cumulative impact estimation**: completing the four refactors above drops site-wide weighted INP by 60-75 percent. **Mobile origin p75 INP** drops from 520ms (current per [`crux_inp_p75`](/nerve-centre/kpi-cards/website-performance/click-responsiveness) earlier example) toward 220-280ms, moving from "poor" band into "good" band. CWV pass rate impact: INP portion lifts 6-10 percentage points toward all-three pass rate. Diagnostic flow: 1. **Sort by INP × traffic.** The absolute-slowest URL may not be the highest commercial impact. 2. **Identify shared dominant interactions.** When the same widget pattern (filter, sort, cart-drawer) appears across multiple URLs, a template-level refactor is more efficient. 3. **Profile the slow interaction in DevTools Performance tab.** Capture a real interaction; identify the JS handler causing the long task. 4. **Apply optimisation patterns**: yield to main thread, debounce, virtualise lists, defer non-critical work. Rapid-response playbook: | Time horizon | Action | | -------------- | ----------------------------------------------------------------------- | | First 1 hour | Identify top 3 by INP × traffic; identify dominant interaction per URL. | | First 24 hours | Profile the worst interaction in DevTools; plan the refactor. | | First 7 days | Implement and ship the highest-leverage refactor. | | First 30 days | Field INP fully reflects fix; re-rank. | ## Sibling cards merchants should reference together | Card | Why merchants reach for it | | -------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- | | [`crux_inp_p75`](/nerve-centre/kpi-cards/website-performance/click-responsiveness) | Origin-level INP; this card decomposes by URL. | | [`psi_slowest_lcp_urls`](/nerve-centre/kpi-cards/website-performance/slowest-lcp-urls) | Per-URL ranking for LCP. | | [`psi_worst_cls_urls`](/nerve-centre/kpi-cards/website-performance/worst-cls-urls) | Per-URL ranking for CLS. | | [`psi_all_cwv_pass`](/nerve-centre/kpi-cards/website-performance/all-cwv-pass) | Per-URL all-three CWV pass status. | | [`psi_biggest_regression`](/nerve-centre/kpi-cards/website-performance/biggest-regression) | URLs with biggest INP regression vs prior period. | | [`psi_lab_tbt`](/nerve-centre/kpi-cards/website-performance/page-freeze-time) | Lab Total Blocking Time, the lab approximation of INP. | | [`psi_unused_js`](/nerve-centre/kpi-cards/website-performance/unused-javascript) | JS bundle size correlates with INP; reducing unused JS reduces interaction cost. | | [`psi_third_party_cost`](/nerve-centre/kpi-cards/website-performance/third-party-cost) | Third-party scripts often contribute to interaction slowness. | | [`psi_js_execution`](/nerve-centre/kpi-cards/website-performance/js-execution-time) | Total JS execution time. | | [`crux_inp_distribution`](/nerve-centre/kpi-cards/website-performance/responsiveness-distribution) | Distribution of INP values across users. | | [`psi_perf_score_summary`](/nerve-centre/kpi-cards/website-performance/performance-score-summary) | Composite score; TBT (lab INP proxy) is 30 percent of the weight. | ## Reconciling against the vendor's own dashboard **Where to look:** * **[Web Vitals Chrome extension](https://chrome.google.com/webstore/detail/web-vitals/ahfhijdlegdabablpippeagghigmibma)**, measures INP per-interaction live; the most useful diagnostic tool. * **Chrome DevTools → Performance tab**, capture interactions; long tasks visible in Bottom-Up view. * **Chrome DevTools → Performance Insights tab**, surfaces INP for specific interactions during recording. * **CrUX URL-level dataset**, for high-traffic URLs, field INP per URL. **Why the Vortex IQ ranking may differ from real-user measurement:** | Reason | Direction | What to do | | --------------------------------------------------------------------------------------------------------------------- | ---------------------- | ---------------------------------------------------------------------------- | | **Lab vs field.** Lab uses TBT as a proxy for INP; field measures actual interactions. | Different metric basis | Confirm with field-data CrUX URL-level when available. | | **Interaction selection.** The audit captures specific interactions; real users may interact with different elements. | Either direction | Add manual interaction profiling for critical user paths. | | **Device profile.** Lab uses mid-tier mobile; some users have faster or slower devices. | Either direction | The mid-tier emulation represents the average; field shows the distribution. | **Cross-connector reconciliation:** primarily internal (with [`crux_inp_p75`](/nerve-centre/kpi-cards/website-performance/click-responsiveness), [`psi_lab_tbt`](/nerve-centre/kpi-cards/website-performance/page-freeze-time), [`psi_third_party_cost`](/nerve-centre/kpi-cards/website-performance/third-party-cost)). **Quick rule for support tickets:** if a merchant says *"my collection page feels fast but you say INP is 720ms"*, the merchant is likely on a faster device than mid-tier emulation. Use Chrome DevTools' CPU throttling (4x slowdown) to approximate the real-user experience. ## Known limitations / merchant FAQs **My top INP URL is a high-traffic page but I can't change the framework. What can I do?** Most INP fixes don't require framework changes. Common patterns: (1) **Debounce rapid input** (filter checkboxes, search-as-you-type); (2) **Yield to the main thread** between heavy work using `setTimeout(fn, 0)` or `scheduler.postTask`; (3) **Defer analytics tracking** to `requestIdleCallback`; (4) **Virtualise long lists** so re-render cost is bounded by viewport. None of these require switching frameworks. **Why does the homepage have a 720ms INP when I rarely touch the currency switcher?** INP is reported as the longest interaction during the session. If a single user happens to use the currency switcher, that 720ms gets reported even though most users never touch it. **Field INP includes the worst case**, not just typical. The fix: optimise the worst-case interaction even if it's used by few users. **Can Vortex IQ tell me exactly which JS function is slow?** Indirectly. The card identifies the dominant interaction; profiling in DevTools Performance tab surfaces the specific function. Lighthouse's audit JSON includes the script URL where the long task occurred but not the function name (without source maps). **Should I refactor the filter widget or replace it entirely?** Depends on engineering bandwidth. **Refactor (1-2 weeks)**: debounce, virtualise, defer analytics. Typically saves 60-70 percent of the interaction cost. **Replace (4-8 weeks)**: switch from JS-driven filter to URL-driven filter (each filter click is a new page navigation rather than client-side re-render). Slightly slower per-click but architecturally simpler and indexable. The right choice depends on the brand's stage and engineering team. **My BC site uses Catalyst not Stencil. Does this still apply?** Yes, with different patterns. Catalyst sites typically have lower baseline INP (better state management, automatic code-splitting); the worst-INP URLs tend to be search results and complex PDPs with many configurable options. The card surfaces them; the fix patterns (yield to main thread, virtualise lists) apply equivalently. **Can Vortex IQ refactor the widget for me?** Read-only by design. Vortex IQ identifies issues; engineering implements. *** ### Tracked live in Vortex IQ Nerve Centre *Worst INP URLs* 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.