Web page evidence capture API with timestamp

What you get

• The rendered page as HTML and a full-page PNG screenshot, both from one page load
• SHA-256 hashes of both artifacts and links to download them
• An OpenTimestamps anchor of the proof digest

Parameters

• urlstringrequiredbody

  Public http(s) URL to capture

  1–2048 characters

Try it

curl -X POST "https://402check.com/v1/proof" \
  -H "Authorization: Bearer rk_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com/"}'

Example response

{
  "id": "01M5YCTV80A6V3J9N5RXW7TC8E",
  "url": "https://example.com/page",
  "capturedAt": "2026-10-27T10:00:00.000Z",
  "sha256": {
    "html": "28c6b4d8ba18e876196fb1d376671e3be48b283f8c1fe6e2481ec62f66b9664e",
    "png": "4353a1de7e0dcc4e87350e22d5c9ee9f3e70e8ce9c31533ec991bee8870c4814"
  },
  "artifacts": {
    "html": "https://402check.com/v1/proof/01M5YCTV80A6V3J9N5RXW7TC8E/html",
    "png": "https://402check.com/v1/proof/01M5YCTV80A6V3J9N5RXW7TC8E/png"
  },
  "anchor": {
    "provider": "opentimestamps",
    "otsBase64": "APAQqrvM",
    "status": "pending"
  }
}

Output against our capture test fixture; ids and hashes come from that run.

HTTP

curl -X POST "https://402check.com/v1/proof" \
  -H "Authorization: Bearer rk_YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com/"}'

MCP

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "proof_create",
    "arguments": {
      "url": "https://example.com/"
    }
  }
}

Endpoint https://402check.com/mcp. Setup for Cursor, Claude and other clients is in the docs.

Source and limits

Data from Cloudflare Browser Rendering and OpenTimestamps.

• Not part of the free tier: it needs a credits key or x402
• Public http(s) URLs only; private and local addresses are refused with 400 invalid_url
• The HTML hash covers the serialized DOM after rendering, not the raw HTTP bytes
• The anchor starts as pending; upgrading it to confirmed is not implemented in v1

Questions