[ 'capture_peer_cert' => true, 'verify_peer' => false, 'verify_peer_name' => false, ] ]); $client = @stream_socket_client( "ssl://{$host}:443", $errno, $errstr, 10, STREAM_CLIENT_CONNECT, $context ); if (!$client) { $error = "Could not connect to " . h($host) . " on port 443. The server may not support SSL/TLS or is not reachable."; } else { $params = stream_context_get_params($client); $cert = openssl_x509_parse($params['options']['ssl']['peer_certificate'] ?? ''); fclose($client); if (!$cert) { $error = "SSL certificate could not be read."; } else { $valid_from = date('d.m.Y', $cert['validFrom_time_t']); $valid_to = date('d.m.Y', $cert['validTo_time_t']); $days_left = (int)(($cert['validTo_time_t'] - time()) / 86400); $is_valid = $days_left > 0; $san = []; if (isset($cert['extensions']['subjectAltName'])) { preg_match_all('/DNS:([^,\s]+)/', $cert['extensions']['subjectAltName'], $m); $san = $m[1]; } $result = [ 'host' => $host, 'cn' => $cert['subject']['CN'] ?? '–', 'issuer' => $cert['issuer']['O'] ?? ($cert['issuer']['CN'] ?? '–'), 'issuer_cn' => $cert['issuer']['CN'] ?? '–', 'valid_from' => $valid_from, 'valid_to' => $valid_to, 'days_left' => $days_left, 'is_valid' => $is_valid, 'san' => $san, 'serial' => $cert['serialNumberHex'] ?? '–', 'algo' => $cert['signatureTypeSN'] ?? '–', 'version' => ($cert['version'] ?? 0) + 1, ]; } } } require_once __DIR__ . '/header.php'; ?>
Tool
SSL Check
Analyze SSL/TLS certificate of a website
Status
0 ? $result['days_left'] . ' days' : 'Expired' ?>
Expires in
Issuer
SAN Domains
Certificate Details
Domain
Common Name (CN)
Issuer
Issuer CN
Valid from
Valid until
Days remaining 0 ? $result['days_left'] . ' days' : 'Expired' ?>
Serial number
Algorithm
VersionTLS v
SAN Domains ()
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Enter a URL or domain to check the SSL certificate. Works without https:// too.
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What is an SSL certificate?

An SSL/TLS certificate is a digital document that confirms the identity of a website and enables encrypted data transmission. The "https://" in the address bar indicates that a secure connection exists. Important components: The CN (Common Name) specifies which domain the certificate was issued for. The CA (Certificate Authority) is the trusted entity that issued the certificate (e.g. Let's Encrypt, DigiCert). SAN entries (Subject Alternative Names) list all domains for which the certificate is valid.