502 Bad Gateway

What HTTP 502 Bad Gateway Means

The server received an invalid response from the upstream server.

Gateway/proxy received invalid response from upstream server.

Common Causes

• Upstream server down
• PHP-FPM not running
• Application server crashed
• Network issue between servers
• Firewall blocking connection

How to Fix It (For Visitors)

• Refresh the page
• Try again in a few minutes
• Contact website administrator

How to Fix It (For Developers/Admins)

• Check upstream server status
• Restart PHP-FPM/application server
• Check Nginx proxy_pass configuration
• Verify firewall rules
• Check application server logs
• Increase timeout settings

Returning a 502 Bad Gateway (Code Examples)

If you build APIs or web apps, here is how to send an HTTP 502 response and how to test for it:

Node.js (Express)

app.get('/resource', (req, res) => {
  res.status(502).json({ error: 'Bad Gateway' });
});

Python (Flask)

@app.route('/resource')
def resource():
    return jsonify(error='Bad Gateway'), 502

PHP

<?php
http_response_code(502);
header('Content-Type: application/json');
echo json_encode(['error' => 'Bad Gateway']);

Check the status with curl

curl -I https://example.com/resource
# Look for: HTTP/1.1 502 Bad Gateway

Frequently Asked Questions

What does HTTP 502 Bad Gateway mean?

Gateway/proxy received invalid response from upstream server. In short: The server received an invalid response from the upstream server.

Is a 502 Bad Gateway error my fault or the website's?

502 is a 5xx server-error code, so the problem is on the server side, not your browser or device. As a visitor you can usually only retry; if you run the site, investigate the server.

How do I fix a 502 Bad Gateway error?

Check upstream server status. Restart PHP-FPM/application server. Check Nginx proxy_pass configuration.

Official Specification

The 502 Bad Gateway status code is defined in RFC 7231 Section 6.6.3.

View the IANA HTTP Status Code Registry →