Checks if a given web address is currently online and reachable.
Checks whether a website or web address is currently reachable and reports how fast it responded.
https://url-uptime-checker.underscoredone.com/check$0.01 per request — pay via x402/USDC. No account needed.
Call this before treating any URL as reachable. Pass the full web address including http:// or https://. Read the 'up' field for a simple yes/no, 'status_code' for the response code, 'response_time_ms' for speed, and 'error' for the reason if it failed. Do not retry automatically on timeout unless explicitly instructed.
| Name | Type | Required | Description |
|---|---|---|---|
url | string | yes | The full web address to check, starting with http or https. |
follow_redirects | boolean | no | Whether to follow the site to its final address if it sends you somewhere else, before reporting the result. |
method | string | no | Which kind of check to run. GET reads the whole page. HEAD only checks that the site answers, which is quicker. |
{
"api_version": "1.0.0",
"url": "https://example.com",
"up": true,
"status_code": 200,
"response_time_ms": 184,
"final_url": "https://example.com/",
"redirected": false,
"error": null,
"checked_at": "2026-07-23T04:12:09Z"
}| Status | Meaning |
|---|---|
400 | Bad request — your input failed validation or could not be processed. Check the detail field for specifics. |
402 | Payment required. Send a signed USDC payment on Base Mainnet or Solana Mainnet using the x402 protocol. |
422 | Unprocessable — a required field is missing or the wrong type. Check the detail field for specifics. |