Page Speed Checklist Tool

Why Page Speed Directly Affects Your Google Rankings

Google introduced page speed as a ranking signal for desktop in 2010 and extended it to mobile in 2018. In 2021, the Page Experience update made Core Web Vitals an official ranking factor, tying Largest Contentful Paint (LCP), Cumulative Layout Shift (CLS), and Interaction to Next Paint (INP) directly to where your pages appear in search results.

LCP measures how quickly the largest visible element loads. It should be under 2.5 seconds. CLS measures how much the page shifts as it loads. It should be under 0.1. INP measures responsiveness to clicks and taps. It should be under 200ms. Pages that fail these thresholds are at a ranking disadvantage against faster competitors, even if their content is stronger.

Beyond rankings, speed affects revenue. Studies consistently show that a one-second delay in page load time reduces conversions by 7% and increases bounce rate significantly. For e-commerce and lead generation sites, speed is one of the highest-ROI technical investments you can make.

Render-Blocking Resources: The Most Common Speed Killer

When a browser encounters a script or stylesheet in the document head, it stops rendering the page and waits for that resource to download and process. This is called render-blocking, and it is the most common speed issue on real websites.

For JavaScript: Add defer to scripts that should run after the DOM is built. Add async to independent scripts. Move any remaining scripts before the closing body tag. Never leave a plain script tag in the head unless it is absolutely critical for first paint.

For CSS: Inline the styles needed for above-the-fold content directly in the head. Load the full stylesheet asynchronously. Use a single combined stylesheet rather than multiple separate files. Tools like Critical or PurgeCSS help automate this process.

Image Optimisation: The Biggest Payload on Most Pages

Images account for over 50% of total page weight on the average website. Unoptimised images are the single largest opportunity for speed improvement on most sites. Our checklist covers three key image factors: format, lazy loading, and explicit dimensions.

Next-gen formats: WebP delivers 25-35% smaller files than JPEG at equivalent quality. AVIF delivers up to 50% savings. Both are supported in all modern browsers. Serve WebP or AVIF with a JPEG fallback using the HTML picture element.

Lazy loading: Add loading="lazy" to all images that are not visible in the initial viewport. Width and height attributes: Always specify them on img elements to prevent layout shift (CLS).

Caching, Compression, and TTFB: Your Server Speed Checklist

Server-side performance sets the baseline for every other speed metric. Even perfectly optimised front-end code cannot compensate for a slow server. Three server-level checks have the biggest impact: TTFB, compression, and caching headers.

TTFB should be under 200ms. High TTFB is usually caused by slow database queries, no full-page caching, or a geographically distant server. Gzip or Brotli compression reduces transfer size by 60-80%. Cache-Control headers prevent browsers from re-downloading unchanged resources on repeat visits.

Resource Hints That Cut Load Time Without Code Changes

Resource hints are single HTML tags that tell the browser to start connecting to, or downloading, resources earlier than it otherwise would. They require no changes to your server or CDN and can meaningfully reduce load time for pages that rely on third-party resources.

preconnect starts the DNS, TCP, and TLS handshake for a third-party origin early. dns-prefetch does only the DNS lookup for less frequently used origins. preload fetches a critical resource at high priority — use it for your LCP image, primary web font, and critical CSS. This is often the fastest single improvement available.