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Resource hint optimization & timing diagnostics

Resource Hint Validator & Preload Checker

Audit your preload, preconnect, dns-prefetch, and prefetch tags. Detect unused preloads, font double downloads, missing crossorigin attributes, and connection latency savings.

  • Unused & redundant preload detection
  • Font CORS double-download check
  • Connection timing & matched request telemetry

Resource Hint Diagnostics

Audit, Validate, and Optimize Resource Directives

Eliminate network waste, prevent duplicate downloads, and accelerate critical asset discovery with automated hint validation.
01

Identify unused preloads and wasted bandwidth

When implemented properly, rel="preload" tells the browser about critical assets discovered late in the document waterfall. However, incorrect file paths, outdated asset hashes, or responsive images loaded only on alternate breakpoints can lead to preloaded files that are never actually used by the page.

Our validator verifies whether every declared preload matches an actual network request executed during page load, flagging unused directives that waste visitor bandwidth and stall other downloads.

02

Prevent font double downloads with CORS validation

One of the most frequent web performance mistakes is preloading web fonts without the crossorigin attribute. Because web fonts are specified by W3C to always load in anonymous CORS mode, preloading without crossorigin causes Chrome and Safari to ignore the preloaded font and download it a second time.

The validator inspects all font preloads for appropriate as="font" and crossorigin configurations, saving hundreds of kilobytes on mobile connections.

03

Uncover high-impact preconnect opportunities

Connecting to third-party origins like Google Fonts, analytics, or external image CDNs requires DNS lookup, TCP handshake, and TLS negotiation. Without a preconnect hint, these connections cannot start until external stylesheets or scripts are downloaded and parsed.

Our tool analyzes the connection timeline of all external domains and recommends targeted rel="preconnect" snippets for origins that delay critical path resources.

Frequently Asked Questions