Resource Hints Auditor

Audit a public web page for resource hints (<link rel="preload">, prefetch, preconnect, dns-prefetch, modulepreload, prerender) in one API call. Returns per-hint analysis, crossorigin gaps, duplicates, a readiness score, letter grade, and Core Web Vitals recommendations. Built for performance engineers, SEO teams, and site migration QA.

Use cases

• Performance engineers - verify preload, preconnect, and dns-prefetch hints are present and correctly configured before launches
• SEO teams - confirm resource hints survive CMS template changes and migrations
• Site migration QA - catch missing or broken resource hints when moving between frameworks, CDNs, or edge providers
• Frontend platform teams - monitor for duplicate hints, missing crossorigin attributes, and preload without as attributes
• Agency consultants - batch-audit client pages and return structured recommendations

Input

Field	Type	Required	Default	Description
startUrl	string	yes	-	Public page URL to audit
timeoutSeconds	integer	no	10	Per-request timeout (3-30 seconds)
maxHtmlBytes	integer	no	1048576	Maximum HTML body size to download and parse (16 KB - 2 MB)

Example input

{
  "startUrl": "https://example.com",
  "timeoutSeconds": 10,
  "maxHtmlBytes": 1048576
}

Output

A single dataset item with the full audit:

Field	Type	Description
inputUrl	string	The URL provided as input
finalUrl	string	Final URL after redirects
https	boolean	Whether the final response was served over HTTPS
hintCount	integer	Total number of resource hint link tags found
byType	object	Count of hints grouped by rel type (preload, prefetch, preconnect, dns-prefetch, modulepreload, prerender)
hints	array	Per-hint analysis (see below)
issues	array	Aggregated issue descriptions across all hints
score	integer	Resource hints readiness score (0-100)
grade	string	Letter grade (A+, A, B, C, D, E, F)
checkedAt	string	ISO 8601 timestamp
recommendations	array	Actionable recommendations for improving resource hints

hints array

Each entry contains:

Field	Type	Description
rel	string	The resource hint rel value (preload, prefetch, preconnect, dns-prefetch, modulepreload, prerender)
href	string	The href attribute value (empty string if missing)
as	string | null	The as attribute value (e.g., font, script, style), or null if absent
crossorigin	string | null	The crossorigin attribute value (anonymous by default), or null if absent
origin	string | null	Resolved origin of the href (protocol + host), or null if unresolvable
issues	array	Issue descriptions for this specific hint
recommendation	string | null	Fix recommendation for this hint (null when the hint is well-formed)

Hint rel types detected

rel	Purpose	Common issues checked
preload	Prioritize late-discovered critical resources	missing as, missing crossorigin for as=fetch
preconnect	Warm TCP/TLS connections to third-party origins	missing crossorigin for cross-origin fonts
dns-prefetch	Resolve DNS for third-party hostnames early	missing href
prefetch	Fetch future-navigation resources during idle time	missing href
modulepreload	Fetch and parse ES modules early	missing href
prerender	Prerender a future page (legacy)	missing href

All hints are also checked for duplicates (same rel + href) and missing href.

Grading scale

Score range	Grade
95-100	A+
85-94	A
75-84	B
65-74	C
50-64	D
30-49	E
0-29	F

Scoring rewards the presence of preload, preconnect, modulepreload, dns-prefetch, and prefetch hints, then subtracts penalties for each issue (missing as, missing crossorigin, duplicates, missing href).

Example output

{
  "inputUrl": "https://example.com",
  "finalUrl": "https://example.com/",
  "https": true,
  "hintCount": 3,
  "byType": {
    "preload": 1,
    "preconnect": 1,
    "dns-prefetch": 1
  },
  "hints": [
    {
      "rel": "preload",
      "href": "/font.woff2",
      "as": "font",
      "crossorigin": "anonymous",
      "origin": "https://example.com",
      "issues": [],
      "recommendation": null
    },
    {
      "rel": "preconnect",
      "href": "https://cdn.example.com",
      "as": null,
      "crossorigin": "anonymous",
      "origin": "https://cdn.example.com",
      "issues": [],
      "recommendation": null
    },
    {
      "rel": "dns-prefetch",
      "href": "//fonts.example.com",
      "as": null,
      "crossorigin": null,
      "origin": "https://fonts.example.com",
      "issues": [],
      "recommendation": null
    }
  ],
  "issues": [],
  "score": 95,
  "grade": "A+",
  "checkedAt": "2026-08-03T12:00:00.000Z",
  "recommendations": [
    "Resource hints look well-structured. Schedule this audit periodically to catch regressions."
  ]
}

Security

• Only public HTTP/HTTPS URLs are accepted
• SSRF protection: localhost, private IPv4/IPv6, and DNS-resolving-to-private IPs are blocked
• URLs with embedded credentials are rejected
• Redirects are manually revalidated before following (max 3)
• HTML body is capped at maxHtmlBytes to prevent oversized responses
• No browser automation, no proxies, no cookies stored

Pricing

Pay per event:

Event	Price
Actor start	$0.005
Page audited	$0.01

A single-page audit costs approximately $0.015.

FAQ

What are resource hints? Resource hints are <link> elements in the HTML <head> that tell the browser to perform networking or fetching work early: preload, prefetch, preconnect, dns-prefetch, modulepreload, and prerender. They improve Core Web Vitals by reducing latency for critical resources.

How is this different from a general SEO meta tags auditor? A meta tags auditor checks title, description, Open Graph, Twitter Card, and canonical tags. This actor focuses exclusively on resource hints and their performance-critical attributes (as, crossorigin, duplicates, missing href), whichgeneric metadata actors do not cover.

Does the actor check the HTTP Link response header for preload? No. This actor parses <link> tags in the HTML body only. Some servers send Link: <...>; rel=preload; as=font in response headers; that is a separate delivery mechanism. A dedicated preload-link-header auditor is a possible future actor.

Can I audit multiple pages in one run? This actor audits one page per run. For bulk audits, schedule multiple runs.

Does the actor follow redirects? Yes, up to 3 redirects. Each redirect target is revalidated for SSRF safety before it is followed.