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name: html-resource-hints description: "Use when reviewing templates, rendered HTML, or shared components related to Add resource hints (preload, prefetch, dns-prefetch). Validate the final browser-facing markup, not just the source framework abstraction." metadata: category: html priority: high difficulty: intermediate estimatedTime: "20" source: frontendchecklist.io url: https://frontendchecklist.io/en/rules/html/html-resource-hints

Add resource hints (preload, prefetch, dns-prefetch)

The browser's HTML parser discovers resources sequentially — a font referenced in a CSS file won't be fetched until the CSS is parsed. Resource hints break this dependency chain, allowing the browser to start fetching critical resources in parallel with parsing. A single preload directive for a critical font can eliminate a 100–300ms Flash of Invisible Text.

Quick Reference

• preload forces immediate download of resources needed by the current page
• prefetch fetches resources likely needed for the next navigation (low priority)
• dns-prefetch resolves DNS for third-party origins in advance
• preconnect does DNS + TCP + TLS for origins you'll connect to soon

Check

Look at this HTML file for late-discovered critical resources — fonts referenced in CSS, hero images, and key scripts. Identify where preload or preconnect hints would help.

Fix

Add appropriate preload hints for critical fonts, images, and scripts. Add preconnect for third-party domains used early in the page.

Explain

Explain each resource hint type (preload, prefetch, preconnect, dns-prefetch), when to use each, and the consequences of misusing them.

Code Review

Review templates, server-rendered HTML, and shared components that output markup related to Add resource hints (preload, prefetch, dns-prefetch). Flag exact elements, attributes, and routes where the rendered HTML violates the rule.

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For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/en/rules/html/html-resource-hints