Page Speed Myths Debunked

The web performance community has its share of myths, half-truths, and outdated advice. Let's separate fact from fiction.

Myth 1: "A Perfect 100 Lighthouse Score Is the Goal"

Reality: A 100 is nice for bragging rights but often not worth the effort. Going from 90 to 100 provides minimal user experience improvement. Going from 40 to 70 is transformative.

The truth:

• Lighthouse scores above 90 provide diminishing returns
• Real-user experience matters more than lab scores
• A score of 75-85 with great UX beats 100 with stripped-down design
• Focus on Core Web Vitals (LCP, INP, CLS) not the composite score

Myth 2: "Just Add a CDN and You're Fast"

Reality: A CDN improves TTFB and static asset delivery, but won't fix:

• Heavy JavaScript bundles (still need to download and execute)
• Unoptimized images (CDN serves them faster, but they're still big)
• Render-blocking resources
• Poor server-side code
• Layout shifts

CDN impact on a slow site:

Metric	Before CDN	After CDN	Real Fix
TTFB	800ms	200ms	✅ Improved
LCP	4.5s	3.8s	❌ Still poor
TBT	1200ms	1200ms	❌ Unchanged
Page weight	3MB	3MB	❌ Unchanged

Myth 3: "HTTP/2 Makes Bundling Unnecessary"

Reality: HTTP/2 reduces the cost of multiple requests, but bundling still matters:

• Each file still has compression overhead
• JavaScript files still need parsing and compilation
• HTTP/2 prioritization can cause issues with many small files
• Modern best practice: strategic code splitting (not one giant bundle, not 100 tiny files)

Myth 4: "Lazy Loading Everything Makes Your Site Faster"

Reality: Lazy loading below-fold images is great. But lazy loading everything backfires:

• Lazy loading the LCP image makes LCP worse (waits for JS to trigger load)
• Lazy loading above-fold content causes visible loading delays
• Over-aggressive lazy loading creates poor UX (content popping in as you scroll)

Best practice:

• Eagerly load above-fold images (especially the LCP element)
• Lazy load below-fold images
• Never lazy load critical text or interactive elements

Myth 5: "Mobile and Desktop Scores Should Be the Same"

Reality: Mobile scores are almost always lower because Lighthouse mobile simulation uses:

• Moto G Power (mid-tier CPU) — 4x CPU throttling
• Slow 4G — 1.6Mbps throughput, 150ms RTT
• Smaller viewport — different layout, potentially different content

Typical score difference: 20-40 points between desktop and mobile. A desktop score of 95 with mobile score of 65 is completely normal.

Myth 6: "Server-Side Rendering Is Always Faster"

Reality: SSR improves perceived speed (content visible sooner) but:

• Increases TTFB (server must render HTML before sending)
• Total page weight may be the same or higher (HTML + JS for hydration)
• Time to Interactive can be worse if hydration is expensive
• Static generation (SSG) is faster than SSR in most cases

Myth 7: "Google Will Penalize You for Slow Speed"

Reality: Core Web Vitals are a minor ranking signal. Google has stated:

• Content relevance matters far more than speed
• CWV is a tiebreaker, not a primary factor
• A slow page with great content will outrank a fast page with poor content
• However, CWV is becoming more important over time

What's real: Speed indirectly affects SEO through:

• Higher bounce rates (user signals)
• Lower crawl efficiency
• Mobile usability issues

Myth 8: "AMP Is Required for Mobile Speed"

Reality: AMP (Accelerated Mobile Pages) is essentially dead:

• Google removed AMP preference from Top Stories (2021)
• AMP provides no ranking advantage
• AMP pages are limited in functionality
• Modern frameworks (Next.js, Astro) achieve the same or better speeds without AMP restrictions

Myth 9: "You Need to Remove All JavaScript"

Reality: JavaScript isn't inherently bad. Unnecessary JavaScript is bad:

• Interactive features require JavaScript
• Framework hydration enables modern UX
• Analytics need JavaScript
• The goal: ship only the JavaScript you need, defer what you can

Targets:

• Marketing site: <100KB total JS
• Web application: <200-300KB initial JS (with code splitting)
• E-commerce: <150KB initial JS

Myth 10: "Performance Optimization Is a One-Time Project"

Reality: Performance degrades naturally over time:

• New features add code
• Marketing adds tracking scripts
• Content grows (more images, more pages)
• Dependencies update
• Third-party scripts change

Performance is a practice, not a project. Monthly audits and continuous monitoring are essential.

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