API Documentation

Overview

301check.com provides a free HTTP redirect chain API that you can integrate directly into your own applications. No registration, no API key — just make a POST request and get results.

Endpoint

Request format

Headers

Content-Type: application/json

Body

{
  "url": "https://example.com",
  "lang": "en"
}

Parameters

• url (required) — the URL to check; HTTP and HTTPS both supported
• lang (optional) — language for error messages: en or zh. Defaults to auto-detection via Accept-Language.

Response format

Success

{
  "success": true,
  "timestamp": "2026-02-22T10:00:00+08:00",
  "inputUrl": "https://example.com",
  "finalUrl": "https://www.example.com",
  "totalRedirects": 1,
  "totalTime": 0.390,
  "loopDetected": false,
  "maxRedirectsReached": false,
  "redirects": [
    {
      "hop": 1,
      "statusCode": 301,
      "statusMessage": "Moved Permanently",
      "type": "permanent",
      "from": "https://example.com",
      "to": "https://www.example.com",
      "duration": 0.234,
      "ip": "93.184.216.34",
      "server": "nginx/1.18.0",
      "tlsInfo": {
        "protocol": "TLSv1.3",
        "subject": "example.com",
        "issuer": "Let's Encrypt",
        "expires": "2026-04-01"
      },
      "headers": {
        "server": "nginx/1.18.0",
        "location": "https://www.example.com"
      }
    }
  ]
}

Error

{
  "success": false,
  "error": "Invalid URL. Please enter a valid HTTP or HTTPS URL."
}

Code examples

cURL

curl -X POST https://www.301check.com/check.php \
  -H "Content-Type: application/json" \
  -d '{"url":"https://example.com","lang":"en"}'

Python

import requests

resp = requests.post(
    "https://www.301check.com/check.php",
    json={"url": "https://example.com", "lang": "en"}
)
data = resp.json()

if data["success"]:
    print(f"Hops: {data['totalRedirects']}, Final: {data['finalUrl']}")
    for hop in data["redirects"]:
        print(f"  {hop['hop']}. {hop['statusCode']} {hop['from']}")
else:
    print("Error:", data["error"])

JavaScript

const res = await fetch('https://www.301check.com/check.php', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ url: 'https://example.com', lang: 'en' })
});
const data = await res.json();
if (data.success) {
  console.log(`${data.totalRedirects} hops → ${data.finalUrl}`);
  data.redirects.forEach(h => console.log(`  ${h.hop}. ${h.statusCode} ${h.from}`));
}

PHP

<?php
$ch = curl_init('https://www.301check.com/check.php');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => json_encode(['url' => 'https://example.com', 'lang' => 'en']),
    CURLOPT_HTTPHEADER => ['Content-Type: application/json'],
]);
$data = json_decode(curl_exec($ch), true);
curl_close($ch);
echo $data['success'] ? $data['totalRedirects'] . " hops\n" : $data['error'] . "\n";
?>

Rate limits

• Per IP: 5 requests per 10 seconds
• When exceeded: HTTP 429 with a bilingual error message

Error handling

Always check the success field. Possible error conditions:

• Invalid or missing URL
• Rate limit exceeded
• Connection timeout (15s)
• DNS resolution failure
• Private/internal IP address blocked