Performance

Preload / Prefetch Checker

Detect missing preload, prefetch, and preconnect hints to improve page loading performance.

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Preload / Prefetch Checker – Detect Missing Resource Hints for Better Performance

The Preload / Prefetch Checker helps you analyze how a web page uses modern browser resource hints such as preload, prefetch, dns-prefetch, and preconnect. These hints allow browsers to fetch critical or future resources earlier, improving load speed, perceived performance, and user experience. This tool identifies missing or underused hints and provides actionable recommendations for performance optimization.

What Are Preload and Prefetch Hints?

Preload and prefetch are browser resource hints that tell the browser how and when to fetch assets. Preload is used for critical resources needed immediately, while prefetch is used for resources that may be needed soon, such as assets for the next page the user is likely to visit.

Understanding rel="preload"

The preload hint is designed for critical resources such as CSS, fonts, or hero images. By preloading these assets, the browser can prioritize them early in the loading process, reducing render-blocking delays and improving metrics like Largest Contentful Paint (LCP).

Understanding rel="prefetch"

Prefetch hints instruct the browser to fetch resources in the background during idle time. These resources are not needed immediately but are likely to be used soon, such as scripts or pages linked in primary navigation.

DNS Prefetch and Preconnect

DNS-prefetch resolves domain names early, while preconnect establishes early connections (DNS, TCP, and TLS) to third-party origins. These hints are especially useful for fonts, analytics, ads, and CDN-hosted assets.

Why Resource Hints Matter for Performance

Proper use of resource hints can significantly reduce time-to-first-byte delays, improve render speed, and enhance overall page responsiveness. They are an important part of modern performance optimization strategies.

How the Preload / Prefetch Checker Works

This tool fetches the HTML of a given page and scans it for link tags using preload, prefetch, dns-prefetch, and preconnect. It then reports what is present, what is missing, and how the configuration could be improved.

Common Performance Issues This Tool Detects

Missing preload hints for critical CSS or fonts
No prefetch hints for likely next navigation
Third-party domains without dns-prefetch or preconnect
Over-reliance on blocking resource loading

SEO and Core Web Vitals Impact

While resource hints are not direct ranking factors, they influence Core Web Vitals such as LCP and INP. Better performance leads to improved user experience, which indirectly supports SEO goals.

Best Practices for Using Preload and Prefetch

Use preload sparingly for truly critical assets. Always include the correct `as` attribute. Use prefetch for likely next actions, and use dns-prefetch or preconnect for third-party origins that affect rendering.

Who Should Use This Tool?

This tool is useful for SEO professionals, developers, performance engineers, and site owners who want to optimize page loading behavior and diagnose performance bottlenecks.

Final Thoughts

Preload and prefetch hints are powerful but often overlooked performance optimizations. The Preload / Prefetch Checker helps you audit these hints quickly and apply best practices to improve speed, usability, and technical SEO quality.

FAQ

What does this tool check?

It checks for preload, prefetch, dns-prefetch, and preconnect hints in page HTML.

Does preload improve SEO?

Indirectly. It improves performance metrics that affect user experience.

Is prefetch safe to use?

Yes, when used correctly for likely next resources.

Can overusing preload hurt performance?

Yes. Overuse can waste bandwidth and delay critical rendering.

Does the tool use third-party APIs?

No. It fetches page HTML directly.

Should every page use preload?

No. Only critical resources should be preloaded.

What is the difference between dns-prefetch and preconnect?

DNS-prefetch resolves domains early, while preconnect also opens TCP/TLS connections.

Is this tool useful for Core Web Vitals audits?

Yes. It helps identify optimizations related to LCP and load speed.

Do browsers support these hints?

Modern browsers support preload, prefetch, dns-prefetch, and preconnect.

Can I use this tool on any URL?

Yes, as long as the page allows fetching HTML.

Related tools

Pro tip: pair this tool with YouTube Keywords Extractor and AI Keyword Cluster Ideas for a faster SEO workflow.