If you care about growth, you care about speed. Fast experiences reduce friction, lift conversions, and cut acquisition costs. So, why is site speed important? Because every extra second makes more users abandon the journey you paid to start.
What is page speed, really?
“Speed” isn’t a single number. It’s a set of user-centric moments that describe how quickly people can see, use, and trust your page.
- Time to First Byte (TTFB): how fast the server starts responding.
- First Contentful Paint (FCP): when something meaningful first appears.
- Largest Contentful Paint (LCP – Core Web Vital): when the main content becomes visible.
- Interaction to Next Paint (INP – Core Web Vital): how responsive the page feels when users interact.
- Cumulative Layout Shift (CLS – Core Web Vital): visual stability (no surprising jumps).
If you’re ever asked what is page speed, answer: “the timeline of how quickly users can see, interact, and trust the page.”
Why speed moves business metrics
- Conversion & revenue: Faster experiences reduce bounce and cart abandonment, especially on mobile and low-bandwidth networks.
- Customer satisfaction: Perceived quality rises with quick feedback; support tickets fall when actions feel instant.
- Paid media efficiency: Speed affects post-click experience and can influence ad Quality Score, dropping CPA.
- SEO impact: Google evaluates page experience signals, so page speed and SEO are linked—better Core Web Vitals improve competitiveness in organic search.
- International growth: Different regions, devices, and networks produce different website speeds; slow locales often hide your next growth tier.
Speed targets that align teams
Use the Core Web Vitals thresholds (measured at the 75th percentile of page loads) as shared goals:
- LCP: Good < 2.5 s; Needs improvement 2.5–4.0 s; Poor > 4.0 s
- INP: Good < 200 ms; Needs improvement 200–500 ms; Poor > 500 ms
- CLS: Good < 0.1; Needs improvement 0.1–0.25; Poor > 0.25
These thresholds translate “how important is website speed?” into objective, cross-functional SLAs.
How to measure website speed
1) Field data
Field—or RUM (Real User Monitoring)—captures the loading speed of a website under actual conditions: devices, networks, geos, and user behavior.
- Search Console → Core Web Vitals: Aggregated field data from Chrome UX Report (CrUX), grouped by URL patterns; ideal for spotting template-level issues.
- CrUX via BigQuery or dashboards: Market-level benchmarks to see how you stack up.
- Product analytics / RUM tools: Stream Core Web Vitals per session to correlate speed with conversion and retention. (Keep the focus on measurement, not implementation.)
How to use field data
- Track p75 for LCP/INP/CLS across key templates (home, PLP, PDP, article, checkout).
- Segment by device, geography, traffic source, and new vs. returning users.
- Tie p75 buckets to outcomes (conversion rate, AOV, lead quality).
2) Lab data
Lab tests simulate loads in a repeatable environment for diagnosis and regression checks.
- Lighthouse / WebPageTest: Run scripted tests for critical pages using consistent device and network profiles; store scores over time.
- Change detection: Compare before/after releases, track deltas, alert on regressions.
How to use lab data
- Maintain a weekly trend of Lighthouse/filmstrips for your top templates.
- Drill into waterfalls and opportunities only to explain field issues—not to prescribe code changes here.
3) Build a speed-to-business view
- Speed distribution, not averages: p50/p75/p90 show how many users suffer—not just “typical” users.
- Attribution by channel: Add speed overlays to acquisition reports to see which website traffic channels send fragile devices or slow networks.
- Conversion curves: Plot conversion rate vs. LCP or INP bins to quantify ROI of improving a template’s p75 by, say, 500 ms.
Reporting that earns buy-in
- Executive KPI: “% of pageviews passing all Core Web Vitals at p75.”
- Operations KPI: “# of pages with Poor LCP” and “# of templates regressed this week.”
- Growth KPI: “Revenue influenced by sessions in Good vs. Poor buckets.”
Answering “how important is website speed” with these three lines makes prioritization straightforward.
Practical prioritization
You don’t need code to decide where speed work pays off first:
- Template × Traffic × Revenue matrix: Rank templates by traffic and revenue share; prioritize the ones with the worst p75.
- Segment stress test: Mobile + top country + top source. That’s where micro-delays compound.
- Checkout & sign-up paths: Evaluate LCP/INP per step; small delays here have outsized impact.
Common pitfalls in measuring speed
- Averages hide pain: Always look at p75 (the standard for Core Web Vitals).
- One-off spikes: PR and launches skew weekly results; annotate big events.
- Ignoring variance by geography: The same page can feel “instant” in Frankfurt and “slow” in Jakarta.
- Equal weighting across pages: Treat revenue-critical pages separately from low-intent pages.
- Confusing lab with field: Lab is for diagnosis; field is your source of truth for real users.
Benchmarks and expectations
There’s no universal magic number, but good programs anchor to:
- >75% of pageviews passing all CWVs at p75 within key markets.
- LCP < 2.5 s for revenue pages on mobile in core countries.
- INP < 200 ms for interactive steps (filters, add-to-cart, form fields).
Adjust targets by channel and device; for example, paid mobile landing pages may require stricter thresholds than blog posts.
Turning insights into action (at a planning level)
Keep it business-first:
- Present the opportunity model (e.g., “Improving PDP LCP from 3.6 s → 2.6 s at p75 is associated with +X% conversion uplift”).
- Align quarterly objectives around a short list of templates and geos.
- Track release impact with side-by-side field metrics; celebrate wins broadly to keep momentum.
Quick glossary for non-engineers
- Core Web Vitals: Google’s trio of user-centric metrics (LCP, INP, CLS).
- Field (RUM) data: Real users, real devices, real networks.
- Lab data: Simulated tests for repeatability and diagnosis.
- p75: The 75th percentile—what most users feel, and the standard for CWVs.
Website speed isn’t a vanity score; it’s a revenue lever. Measure it where it matters (in the field, by template, at p75), connect it to outcomes, and your roadmap will tell you exactly where to focus next.