526 Invalid SSL Certificate

What HTTP 526 Invalid SSL Certificate Means

Cloudflare could not validate the origin server's SSL certificate.

A Cloudflare-specific code: in Full (strict) mode, the origin certificate is expired, self-signed, or otherwise untrusted.

Common Causes

• Expired origin certificate
• Self-signed or untrusted certificate in strict mode
• Hostname mismatch on the certificate
• Incomplete certificate chain

How to Fix It (For Visitors)

• Contact the website owner

How to Fix It (For Developers/Admins)

• Install a valid, trusted certificate (or a Cloudflare Origin CA cert)
• Include the full chain and correct hostnames
• Switch to Full (not strict) only as a temporary measure
• Renew expired certificates

Returning a 526 Invalid SSL Certificate (Code Examples)

If you build APIs or web apps, here is how to send an HTTP 526 response and how to test for it:

Node.js (Express)

app.get('/resource', (req, res) => {
  res.status(526).json({ error: 'Invalid SSL Certificate' });
});

Python (Flask)

@app.route('/resource')
def resource():
    return jsonify(error='Invalid SSL Certificate'), 526

PHP

<?php
http_response_code(526);
header('Content-Type: application/json');
echo json_encode(['error' => 'Invalid SSL Certificate']);

Check the status with curl

curl -I https://example.com/resource
# Look for: HTTP/1.1 526 Invalid SSL Certificate

Frequently Asked Questions

What does HTTP 526 Invalid SSL Certificate mean?

A Cloudflare-specific code: in Full (strict) mode, the origin certificate is expired, self-signed, or otherwise untrusted. In short: Cloudflare could not validate the origin server's SSL certificate.

Is a 526 Invalid SSL Certificate error my fault or the website's?

526 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 526 Invalid SSL Certificate error?

Install a valid, trusted certificate (or a Cloudflare Origin CA cert). Include the full chain and correct hostnames. Switch to Full (not strict) only as a temporary measure.

Official Specification

The 526 Invalid SSL Certificate status code is defined in Cloudflare (non-standard).

View the IANA HTTP Status Code Registry →