Free SSL Certificate Checker - Verify HTTPS Security
Enter any domain to check its SSL/TLS certificate status, expiration date, issuer information, and security rating. Ensure websites are properly secured before entering sensitive data.
Last updated: May 2026
SSL Certificate Checker
Enter a domain name (without https://)
What we check
- Certificate validity and expiration date
- Issuer and certificate chain
- TLS protocol version and cipher suite
- Subject Alternative Names (SANs)
- HSTS header support
- SHA-256 fingerprint
SSL Certificate Details
Your SSL analysis will appear here
Enter a domain and click Check SSL
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Why SSL Certificates Matter
SSL (Secure Sockets Layer) certificates encrypt data transmitted between a user's browser and a website's server. Websites with SSL show 'HTTPS://' in the URL and display a padlock icon. This encryption protects sensitive information like passwords, credit card numbers, and personal data from being intercepted by attackers.
Why SSL Matters for Your Website
Valid SSL is no longer optional. Here is what is at stake if your certificate fails.
1. Google Ranking Signal
Google has used HTTPS as a confirmed ranking signal since August 2014. Sites without valid SSL lose visibility in organic search, especially for commercial queries where trust matters most.
HTTPS is a confirmed Google ranking factor since 2014
2. Chrome Not Secure Warning
Starting with Chrome 68 in July 2018, every page served over plain HTTP shows a "Not Secure" label in the address bar. Expired or invalid certificates trigger a full-page interstitial that blocks visitors from reaching your site.
Chrome marks HTTP as Not Secure since v68 (July 2018)
3. Conversion & Compliance
PCI-DSS 4.0, GDPR, and HIPAA all require encryption of data in transit. Beyond compliance, studies show 85% of online shoppers abandon a purchase if the browser warns them about the site's security.
85% of shoppers abandon checkout on insecure sites
Common SSL Errors and How to Fix Them
These six issues account for nearly every SSL certificate problem you will encounter.
Expired Certificate
The not-after date has passed. Browsers show NET::ERR_CERT_DATE_INVALID and block access. Fix by renewing the certificate with your CA or rerunning your Certbot/ACME client.
Self-Signed Certificate
The certificate was signed by the server itself instead of a trusted CA. Common in staging or internal tools. Replace with a free Let's Encrypt certificate via Certbot or a paid certificate from DigiCert.
Hostname Mismatch
The hostname in the URL does not appear in the certificate's Subject Alternative Names. Issue a new certificate that includes every hostname (apex, www, and any subdomains) you serve over HTTPS.
Weak Cipher / SHA-1
Certificates signed with SHA-1 or RSA keys under 2048 bits are rejected by modern browsers. Reissue with SHA-256 or stronger and at minimum 2048-bit RSA (or 256-bit ECDSA).
Missing Intermediate
The server sends only the leaf certificate without the intermediate CA bundle. Mobile browsers and some Linux clients fail to chain to the root. Concatenate the intermediate certificates into your fullchain.pem file.
Mixed Content
The HTML loads over HTTPS but includes images, scripts, or stylesheets over plain HTTP. Chrome blocks all active mixed content. Audit your site for hardcoded http:// URLs and update them to protocol-relative or HTTPS.
How Our SSL Checker Works
A real TLS handshake is the only way to truly verify a certificate. Here is what happens behind the scenes.
TLS Handshake on Port 443
We open a real TLS connection to the hostname you submitted using Node.js native TLS APIs with SNI (Server Name Indication). The server presents its certificate as part of the standard TLS handshake.
Certificate Parsing
We extract subject, issuer, serial number, fingerprints (SHA-256), signature algorithm, public key size, and the not-before / not-after validity window from the X.509 certificate.
Hostname & Chain Validation
We walk the certificate chain from leaf to root, verify the hostname against the Subject Alternative Names (with wildcard support), and confirm the chain terminates at a trusted root CA.
Protocol & HSTS Inspection
We record the negotiated TLS protocol version (TLS 1.2 or TLS 1.3 ideally) and send a separate HEAD request to detect the Strict-Transport-Security response header.
Days-Remaining Health Score
We compute the time-to-expiration and color-code it so you can act before any outage occurs.
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