# URL Uptime Checker

> URL Uptime Checker is a paid API for AI agents from url-uptime-checker.underscoredone.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).

Checks whether a given URL is currently online and reachable, returning status code, response time, and redirect details.

## Facts

- Endpoint: POST https://url-uptime-checker.underscoredone.com/check
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/url-uptime-checker-d37b5734
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_qKqJLAUXjqJut4je8b09L

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability url-uptime-checker-d37b5734 -d '<json body>'
```

Example prompt: Can you check if https://api.myservice.com is currently up and responding — use a HEAD request so it's fast, and follow any redirects to the final destination?

## When to prefer this

Use this endpoint when you need a quick, real-time check of whether a specific URL is reachable from an external vantage point. Ideal for pre-flight checks before scraping, link validation, lightweight health monitoring, or confirming a deployment is live. Prefer this over full monitoring platforms when you only need a single on-demand check rather than continuous polling.

## Known failure modes

- URL is unreachable or DNS fails — 'up' is false with an error message
- Invalid or malformed URL input — API may return an error or treat as down
- Target server responds very slowly causing a timeout — may be reported as down
- URL requires authentication — may return 401/403 but still reported as 'up' depending on status logic
- Network issues on the checker's side — false negatives possible

## How this service works

Checks whether a website or web address is currently reachable and reports how fast it responded.

## Output

A JSON object containing whether the URL is up (boolean), the HTTP status code, response time in milliseconds, the final URL after any redirects, whether a redirect occurred, and the timestamp the check was performed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "description": "The full web address to check, including http:// or https:// at the start."
  },
  "method": {
   "type": "string",
   "description": "Which kind of request to send: 'GET' to fetch the page or 'HEAD' to just check reachability faster. Defaults to 'GET'."
  },
  "follow_redirects": {
   "type": "boolean",
   "description": "Whether to follow redirects to their final destination before reporting the result. Defaults to true."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "up": true,
  "url": "https://example.com",
  "error": "",
  "final_url": "https://example.com/",
  "checked_at": "2026-07-23T04:12:09Z",
  "redirected": false,
  "api_version": "1.0.0",
  "status_code": 200,
  "response_time_ms": 184
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/url-uptime-checker-d37b5734/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from url-uptime-checker.underscoredone.com](https://www.zero.xyz/host/url-uptime-checker.underscoredone.com/llms.txt)