CORS Header Checker — check
Limited track record
How we rate this
Delivery health: unknown. Paid successes: 0. Paid failures: 0. Schema confidence: high.
Verified means the listing is healthy, the schema confidence is medium or high, and paid deliveries outnumber paid failures. Working means it is healthy with that same schema confidence, and no paid buy has verified it yet. Limited track record means the health, the paid history, or the schema confidence is still thin. Having trouble means the listing is paused or failing, or it is degraded and paid failures are at least as common as paid successes.
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.
More
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.
Example
What agents use this for. 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. Category: x402/cors headers.
Request
POST https://cors-header-checker.underscoredone.com/check
curl
curl -sS -X POST \
'https://cors-header-checker.underscoredone.com/check' \
-H 'Content-Type: application/json' \
-d '{"url":"https://bitcoin.org/"}' \
# Example only. No L402 token. Sends no sats.
MCP buy
buy({
"sku": "bazaar-de5f9abf5af9",
"params": {
"url": "https://bitcoin.org/"
}
})
Response
No response schema is listed, and no example sample is stored.
cors-header-checker.underscoredone.com