You redesigned the landing page. You A/B tested the headline. You even rewrote the CTA copy three times. Conversions barely moved. Sound familiar?
The problem might not be what visitors see — it might be what they experience before they see anything at all. Performance issues are invisible to marketers but brutal on conversion rates. Google's own research shows that as page load time goes from 1 second to 3 seconds, the probability of bounce increases by 32%. Push it to 5 seconds and that number jumps to 90%.
Here are five performance killers we find on almost every site we audit — and the fixes that move the needle.
1. Unoptimized Images That Double Your Page Weight
This is the single most common issue we see. A hero image that should be 80KB is served as a 2.4MB PNG. Product images rendered at 4000×3000 when they display at 400×300. No lazy loading, no modern formats, no srcset.
The fix is straightforward but has to be systematic. Convert all images to WebP or AVIF. Serve responsive sizes with srcset and the sizes attribute. Lazy-load anything below the fold. For hero images and LCP elements, use fetchpriority="high" and preload them in the document head.
We routinely see this single change cut page weight by 40–60% and shave 1–2 seconds off load time. That alone can move conversion rates by 5–10%.
2. Render-Blocking Scripts That Freeze First Paint
Every synchronous script in your document head is a toll booth. The browser stops everything — parsing, rendering, painting — until that script downloads and executes. Stack up a tag manager, an analytics snippet, a chat widget, and a consent banner, and you've added seconds of dead time before visitors see anything.
Audit your script tags. Anything that doesn't need to run before first paint should get a defer attribute. Third-party scripts that aren't critical to the initial experience should load asynchronously or be deferred until after interaction. Move non-critical CSS out of the head using media attributes or dynamic injection.
The goal is a clean critical rendering path: only the HTML, CSS, and JavaScript needed for what the user sees first.
3. Layout Shifts That Destroy Trust (and Click Accuracy)
You've experienced this: you're about to tap a button, and the page jumps. An ad loads. An image expands. A font swaps in. You click the wrong thing. Frustrating as a user. Devastating as a business.
Cumulative Layout Shift (CLS) is now a Core Web Vital, and Google uses it as a ranking signal. But beyond SEO, layout shifts directly hurt conversions. When a CTA button moves right as a visitor reaches for it, they either click something else or lose confidence in the page entirely.
Fix it by setting explicit width and height attributes on all images and videos. Use font-display: swap with size-adjusted fallback fonts to minimize font-swap shifts. Reserve space for dynamic content like ads or embeds with aspect-ratio containers. Use the CSS contain property to isolate layout recalculations.
4. Slow Server Response Time (TTFB Over 600ms)
Time to First Byte measures how long it takes your server to start responding. If TTFB is over 600ms, everything else is playing catch-up. No amount of frontend optimization can fix a slow backend.
Common culprits include unoptimized database queries, missing server-side caching, no CDN, and overloaded shared hosting. If your site runs on a CMS like WordPress, uncached dynamic page generation is often the bottleneck.
Start with a CDN for static assets and full-page caching where possible. Enable server-side compression (Brotli over Gzip). Review your hosting plan — if you're on shared hosting and getting real traffic, it's time to upgrade. For dynamic sites, implement application-level caching for expensive database queries.
5. Third-Party Script Bloat You Don't Know About
Tag managers make it dangerously easy to add scripts. Marketing wants a heatmap tool. Sales wants a chatbot. Support wants a feedback widget. Product wants session replay. Before long, your page loads 40 third-party scripts, and nobody owns the performance budget.
Run a third-party audit. Open Chrome DevTools, go to the Network tab, and filter by third-party requests. You'll likely find scripts from tools nobody uses anymore, duplicate analytics implementations, and widgets that load 500KB of JavaScript to show a small icon in the corner.
Remove everything you're not actively using. For the scripts you keep, load them conditionally — chat widgets don't need to load until a user shows intent to interact. Use a performance budget: set a total JavaScript threshold (say, 300KB compressed) and treat it like a deployment gate.
The Compounding Effect
These issues rarely exist in isolation. A site with unoptimized images probably also has render-blocking scripts and no CDN. The performance tax compounds: each issue adds latency, and each additional second of load time has an exponentially larger impact on conversions.
The good news is that the fixes also compound. Address all five, and you're not just incrementally faster — you're delivering a fundamentally different experience. Pages that load in under 2 seconds feel instant. Visitors who don't wait don't bounce. And visitors who don't bounce are visitors who convert.
If you're not sure where your site stands, that's exactly what our audit is built to uncover. We test every page across all of these dimensions and rank every finding by how much revenue it's likely costing you.