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Step-by-step guide for US founders and marketers: measure LCP, INP, CLS, diagnose root causes, prioritise fixes, and validate impact on conversions.
Focus on LCP, INP, CLS, TTFB and business KPIs that map to revenue.
Use a High Impact/Low Effort matrix to sequence fixes that reduce CAC and boost RPV.
Combine lab tests, RUM, and server-side tracking to avoid regressions and preserve attribution.
A website performance audit answers one question: what parts of your site slow down revenue delivery? For US-based eCommerce and B2B sites, speed and reliability directly affect conversion rates, paid media efficiency, and lifetime value. This guide explains how to conduct a website performance audit, how to measure meaningful metrics (not vanity), and how to prioritize fixes that impact acquisition cost (CAC) and margin.
Start with these tools to gather objective data: Google PageSpeed Insights, Lighthouse, WebPageTest, and a real-user monitoring (RUM) provider. For tag and event validation, use GA4 and Google Tag Manager. For Shopify or WordPress stores, pair these with server logs and hosting metrics. Learn more about Prebo Digital's technical-first approach on the Services page to see how audits feed into ongoing optimisation.
| Area | Check | Impact |
|---|---|---|
| Images | Serve next-gen formats, lazy-load below the fold | $ savings via faster page loads and higher conversion |
| Third-party scripts | Audit tag load order; move non-critical tags off the main thread | Reduces main-thread blocking; lowers TTFB |
| Caching & CDN | Verify cache headers and regional CDN edge presence | Improves US-wide performance and ad efficiency |
Consideration: run audits from multiple US locations (East, Central, West) and simulate mobile 4G to match typical user conditions. Differences can change prioritisation.
A performance audit should include an event and conversion check to ensure any front-end changes keep analytics intact. Validate GA4 events, Tag Manager triggers, and server-side endpoints. If you need a technical reference for tracking architecture, see the team overview on About Prebo Digital which covers measurement-first approaches.
Browser -> Network -> CDN -> Origin Server | | | v v v RUM -> GA4 -> Server-side GTM -> Order DB
This diagram highlights where performance issues can break attribution. If the browser fails to send a purchase event due to slow scripts, server-side capture can preserve revenue tracking.
For an example of how audits feed into performance roadmaps and continuous testing, explore Prebo Digital's homepage case examples at Prebo Digital.
Follow a structured process: Discover, Measure, Diagnose, Prioritise, Remediate, and Validate. Below are actionable steps with US-focused examples and rough impact estimates expressed in dollars where appropriate.
Run Lighthouse audits, PageSpeed Insights, and multi-location WebPageTest runs. Combine that with GA4 RUM data to surface real-user distributions for LCP, INP, and CLS. Record median and 75th percentile values for representative pages.
Prioritise fixes by estimated revenue impact and implementation effort. Use a 2x2: High Impact / Low Effort first. Example: image compression is often low effort with measurable uplift; replacing a heavy personalization script may be high effort but necessary for long-term velocity.
| Stage | Focus | Performance metric |
|---|---|---|
| TOF (Top of Funnel) | Landing speed, ad landing experiences | LCP, TTFB |
| MOF (Middle) | Category pages, filters | Time-to-interactive, bundle size |
| BOF (Bottom) | Product pages, cart, checkout | Checkout conversion rate, INP |
Implement fixes in a staging environment, then A/B test critical changes that might affect conversion (for example, moving a script asynchronously). Track both performance metrics and business KPIs in GA4 and in server logs. For iterative optimisation and long-term retention of gains, consider a managed retainer that ties work back to revenue-Prebo Digital outlines service models on the Services page.
Deploy RUM alerts for thresholds (e.g., LCP > 2.5s for 5% of US mobile users) and integrate performance signals into reporting. Re-run synthetic tests after deployments and compare 7-day and 28-day windows to detect regressions.
If you want a practical, revenue-focused performance roadmap tailored to Shopify or WooCommerce, request a technical audit via the Contact page and link audit outcomes to CRO and paid media strategy.
Marion is an award-winning content creator with over a decade of experience crafting high-impact B2B and B2C content strategies. Her content journey began in the mid-00s as a journalist and copywriter, focusing on pop culture, fashion, and business for various online and print publications. As the Content Lead at Prebo Digital, Marion has driven significant increases in engagement, page views, and conversions by employing a creative approach that spans ideation, strategy and execution in organic and paid content.
Disclaimer: This content is for educational purposes only. Product availability, pricing, and specifications are subject to change. Always verify current details on the retailer's website before making a purchase. We may earn affiliate commissions from qualifying purchases.
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