Page Speed Test
Analyze your website's performance using Google Lighthouse. Get scores for Performance, Accessibility, Best Practices, and SEO with detailed optimization opportunities.
“A page that loads in 1 second feels instant. A page that loads in 4 seconds feels broken.”
How It Works
DNS Checker Page Speed Test runs Google Lighthouse audits against your URL from a dedicated server in Ashburn, Virginia (US-East). Each scan performs three full Lighthouse passes on both desktop and mobile viewports, then takes the median result for consistency. This median-of-three approach reduces noise from network jitter and one-off rendering delays, producing scores that closely match what Google PageSpeed Insights reports.
The scan uses a real Chrome browser instance, not a synthetic renderer, so the results reflect actual browser behavior including JavaScript execution, layout shifts, and resource loading. Desktop scans run without throttling. Mobile scans apply CPU slowdown to simulate a mid-range device on a 4G connection.
What DNS Checker Page Speed Test Checks
Performance
Measures how quickly page content loads and becomes interactive. Includes Largest Contentful Paint (LCP), Total Blocking Time (TBT), Cumulative Layout Shift (CLS), First Contentful Paint (FCP), and Speed Index.
Accessibility
Checks whether the page follows web accessibility best practices, including color contrast, ARIA attributes, keyboard navigation, and semantic HTML structure.
Best Practices
Audits for modern web development patterns such as HTTPS usage, safe JavaScript APIs, correct image aspect ratios, and absence of deprecated APIs or console errors.
SEO
Verifies search engine optimization fundamentals including meta tags, crawlable links, valid robots.txt directives, mobile-friendly viewport configuration, and structured data.
Understanding Core Web Vitals
Core Web Vitals are performance metrics that Google uses to evaluate real-world user experience. These metrics directly influence search rankings as part of the page experience signal. Lighthouse measures them in a controlled lab environment to provide consistent, reproducible scores.
LCP
25% weightLargest Contentful Paint
Time until the largest visible content element renders. Typically a hero image or heading.
CLS
25% weightCumulative Layout Shift
Measures unexpected layout movement during page load. Lower is better.
TBT
30% weightTotal Blocking Time
Total time the main thread was blocked for 50ms+ between FCP and TTI.
FCP
10% weightFirst Contentful Paint
Time until the first text or image element renders on screen.
SI
10% weightSpeed Index
How quickly the visible area of the page is populated with content.
Page Speed Optimization Guide
Image Optimization
Images are often the largest resources on a page and the primary contributor to slow LCP. Convert images to modern formats like WebP or AVIF, which offer 25-50% better compression than JPEG. Use responsive srcset attributes so browsers download appropriately sized images for each viewport. Apply lazy loading via the loading="lazy" attribute for images below the fold, and always set explicit width and height attributes to prevent layout shifts.
JavaScript Optimization
Excessive JavaScript is the leading cause of high TBT scores. Implement code splitting to load only the JavaScript needed for the current route. Use tree shaking to eliminate unused code from bundles. Add defer or async attributes to non-critical scripts so they do not block the initial render. Consider lazy-loading heavy components that are not visible above the fold.
CSS Optimization
Render-blocking CSS delays First Contentful Paint. Extract and inline critical CSS needed for above-the-fold content directly in the HTML <head>. Defer loading of the full stylesheet using media queries or JavaScript-based loading. Remove unused CSS rules -- tools like PurgeCSS can reduce stylesheet size by 80-95% for utility-first frameworks.
Server Optimization
A fast Time to First Byte (TTFB) is the foundation of good LCP. Use a CDN to serve assets from edge locations close to the user. Enable Brotli or gzip compression for text-based resources (HTML, CSS, JavaScript, SVG). Serve assets over HTTP/2 or HTTP/3 for multiplexed connections. Set appropriate Cache-Control headers with long max-age values for static assets. The HTTP Security Headers tool can help verify header configuration, and the HTTP Header Checker shows a complete timing waterfall including TLS handshake details.
Font Optimization
Web fonts can cause invisible text (FOIT) or layout shifts (FOUT) if not loaded properly. Set font-display: swap to show a fallback font immediately while the custom font loads. Preload critical font files with <link rel="preload">. Subset fonts to include only the character ranges needed for the page content, which can reduce font file sizes by 70-90%.
Third-Party Script Management
Third-party scripts (analytics, ads, chat widgets, social embeds) often contribute significant main-thread blocking time. Audit third-party impact using the Lighthouse diagnostics panel. Load non-essential third-party scripts after the page becomes interactive. Use loading="lazy" for iframes containing social or video embeds. Consider self-hosting critical third-party resources to reduce DNS lookup and connection overhead -- the DNS Inspector can help identify the DNS resolution chain for any domain.
How Lighthouse Scoring Works
The Lighthouse performance score is a weighted average of five metrics. Each metric is individually scored on a 0-100 scale using a log-normal distribution derived from real-world performance data in the HTTP Archive. The weights are:
TBT
30%
LCP
25%
CLS
25%
FCP
10%
SI
10%
The final score is color-coded into three tiers: green (90-100) indicates good performance with all metrics meeting recommended thresholds; orange (50-89) suggests meaningful optimization opportunities exist; and red (0-49) signals significant performance problems that likely affect user experience and search rankings.
Mobile scores are typically 20-30 points lower than desktop for the same page. This is expected because mobile testing applies 4x CPU throttling and simulates a 4G network connection, which increases all time-based metrics. When evaluating performance, compare mobile scores against other mobile scores, and desktop against desktop.
For a comprehensive view of on-page factors that affect both performance and search visibility, the On-Page SEO Auditor checks 70+ SEO factors including meta tags, heading structure, and content quality.
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