Sends a real request to any URL you provide, attaches an Origin header, and reads back all
Sends a real request to any URL you provide, attaches an Origin header, and reads back all six standard cross-origin permission headers the server returns. Tells you whether cross-origin requests are enabled at all, whether your specific origin is permitted, and shows every permission value exactly as the server sent it. Useful for finding why a browser is blocking a request, confirming a new deployment is configured correctly, or auditing whether a public API allows credentialed calls.
10000 (raw units)
price
3
calls / 30d
3
unique payers
2026-09-14
updated
Provider
cors-header-checker.underscoredone.com · discovered, not yet claimed by its owner
Payment (x402 accepts[])
[
{
"scheme": "exact",
"network": "eip155:8453",
"payTo": "0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08",
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"amount": "10000",
"maxTimeoutSeconds": 300
},
{
"scheme": "exact",
"network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
"payTo": "8ugAWAXDB8V18kiUrGZTq1oMvU3C6Fxs8hfC6rvzQT3b",
"asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
"amount": "10000",
"maxTimeoutSeconds": 300
}
]Output schema
{
"bazaar": {
"info": {
"input": {
"body": {
"origin": "https://myapp.com",
"url": "https://api.github.com"
},
"bodyType": "json",
"method": "POST",
"type": "http"
},
"output": {
"example": {
"api_version": "1.0.0",
"cors_enabled": true,
"error": "",
"headers": {
"access-control-allow-credentials": null,
"access-control-allow-headers": null,
"access-control-allow-methods": null,
"access-control-allow-origin": "https://github.com",
"access-control-expose-headers": "ETag, Link, Location, Retry-After, X-GitHub-OTP, X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Used, X-RateLimit-Resource, X-RateLimit-Reset, X-OAuth-Scopes, X-Accepted-OAuth-Scopes, X-Poll-Interval, X-GitHub-Media-Type, X-GitHub-SSO, X-GitHub-Request-Id, Deprecation, Sunset",
"access-control-max-age": null
},
"origin_allowed": false,
"origin_tested": "https://myapp.com",
"status": 200,
"url": "https://api.github.com"
},
"type": "json"
}
},
"schema": {
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"body": {
"additionalProperties": false,
"properties": {
"origin": {
"description": "The website address you want to test cross-origin access from, for example https://myapp.com. Defaults to https://example.com if you leave it out.",
"type": "string"
},
"url": {
"description": "The full web address of the endpoint you want to check — must start with http:// or https://.",
"type": "string"
}
},
"required": [
"url"
],
"type": "object"
},
"bodyType": {
"enum": [
"json",
"form-data",
"text"
],
"type": "string"
},
"method": {
"enum": [
"POST",
"PUT",
"PATCH"
],
"type": "string"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method",
"bodyType",
"body"
],
"type": "object"
},
"output": {
"properties": {
"example": {
"properties": {
"api_version": {
"type": "string"
},
"cors_enabled": {
"type": "boolean"
},
"error": {
"type": "string"
},
"headers": {
"additionalProperties": true,
"type": "object"
},
"origin_allowed": {
"type": "boolean"
},
"origin_tested": {
"type": "string"
},
"status": {
"type": "integer"
},
"url": {
"type": "string"
}
},
"required": [
"api_version",
"url",
"origin_tested",
"status",
"cors_enabled",
"origin_allowed",
"headers",
"error"
],
"type": "object"
},
"type": {
"type": "string"
}
},
"required": [
"type"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}
}
}Use it
curl
curl "https://cors-header-checker.underscoredone.com/check" # -> 402 Payment Required, accepts[] lists how to pay # retry with a PAYMENT-SIGNATURE (or PAYMENT header) once paid
JavaScript
const res = await fetch("https://cors-header-checker.underscoredone.com/check");
if (res.status === 402) {
const { accepts } = await res.json();
// pay one of accepts[] via an x402 client, then retry with the payment header
}Python
import httpx
res = httpx.get("https://cors-header-checker.underscoredone.com/check")
if res.status_code == 402:
accepts = res.json()["accepts"]
# pay one of accepts[] via an x402 client, then retry with the payment headerMachine-readable
Everything on this page is also available as clean JSON at /resources/3627.json, and this resource appears in /discovery/resources and /discovery/search.