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PerformanceChecked through WebDiag API

Resource Hints Analyzer

Enter a URL to check resource hints in static HTML without a fake performance score or claims that every hint is used by the browser.

  • preconnect / dns-prefetch
  • preload / modulepreload
  • duplicates and attributes
Online tool

Try the tool

Enter a URL: WebDiag will run a safe network check and show the result.

Page URL

Network check through backend

For HTTP/SEO tools, the URL is sent to the WebDiag API, where SSRF protection, DNS/IP policy, and redirect limits are applied.

Reviewed: 2026-07-17
01

How to use it

  1. 1

    Enter a public page URL.

  2. 2

    Run bounded static HTML analysis.

  3. 3

    Review hint counts, duplicates, as values, and crossorigin signals.

02

What the tool can do

  • Supports preconnect, dns-prefetch, preload, prefetch, modulepreload, and literal preinit.
  • Normalizes relative URLs and shows same-host/cross-host signals.
  • Flags duplicate hints, preload without as, and excessive preconnect counts.
03

Common use cases

  • Review the head after frontend performance setup changes.
  • Find excessive preconnects and duplicate preloads.
  • Review crossorigin signals for cross-origin resources.
04

How it works inside

The many-preconnect threshold is a review signal, not a universal browser limit.

Hint effectiveness should be verified with browser profiling and real-user data.

05

Questions and answers

Should every resource be preloaded?

No. Excessive preload competes for bandwidth and priority; use it for measured critical resources.

Why is preconnect without crossorigin flagged?

For some cross-origin fetch modes, a connection without matching crossorigin may not be reusable; this is a review signal, not an automatic error.