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HTTP Header Checker
x402
HTTP Header Checker is a paid API for AI agents from http-header-checker.underscoredone.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).
Fetches and returns the HTTP response headers, status code, redirect chain, and missing security headers for any given URL
Price / call$0.01
Success—
StatusUnknown
How this service works
Sends a request to a web address you provide and reports back everything the server said in response: the status code, all the response headers, how many times it got redirected, and how long the whole thing took.
Output
Returns a JSON object containing the HTTP status code, all response headers as key-value pairs, the final URL after redirects, the full redirect chain with intermediate status codes, response time in milliseconds, and a list of missing security headers such as strict-transport-security and content-security-policy.
Example use cases
Example prompt
“Can you check the HTTP response headers for https://myblog.com — use a GET request and follow any redirects so I can see the final URL, status code, and any missing security headers?”
Technical details
Endpoint
POSThttps://http-header-checker.underscoredone.com/checkWhen to prefer
Use this endpoint when you need to programmatically inspect HTTP response headers, status codes, redirect chains, or security header presence for any URL — especially useful for site audits, security checks, redirect debugging, or verifying CDN/cache configurations. Prefer this over a generic web scraper when you only need header metadata and not page content.
Side effects
- Target URL is unreachable or times out — returns network error or timeout response
- Invalid URL format provided — returns validation error
- URL uses an unsupported scheme — returns error
- Domain does not resolve (DNS failure) — returns connection error
- Target server returns an unexpected non-HTTP response — may return partial or error result
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | The full web address to check, including http:// or https:// |
| method | string | Either GET or HEAD; GET fetches the page normally, HEAD only asks for headers without the body |
| follow_redirects | boolean | Whether to follow redirects to their final destination or stop at the first one |
Output
Schema · Response
{
"type": "json",
"example": {
"url": "https://example.com",
"headers": {
"server": "nginx",
"content-type": "text/html; charset=UTF-8",
"cache-control": "max-age=600",
"content-length": "1256"
},
"final_url": "https://example.com/",
"api_version": "1.0.0",
"status_code": 200,
"redirect_chain": [
{
"url": "http://example.com",
"status_code": 301
}
],
"response_time_ms": 214,
"missing_security_headers": [
"strict-transport-security",
"content-security-policy"
]
}
}Tags
x402
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