SSL Certificate Checker

Verify SSL/TLS certificates for any domain. Check expiry dates, issuer details, SANs, and certificate chain validity instantly.

What Is an SSL Certificate Check?

SSL/TLS certificates are the foundation of secure communication on the web. They encrypt the connection between a visitor's browser and a web server, ensuring that sensitive data like passwords, payment details, and personal information cannot be intercepted by attackers. Every website served over HTTPS relies on a valid SSL/TLS certificate to establish this encrypted channel.

An SSL certificate check connects to a domain's server on port 443, retrieves the live TLS certificate, and validates its details. The check reveals who issued the certificate, which domains it covers, whether the full chain of trust is intact, and how many days remain before it expires.

Domainwise inspects the actual certificate served by the server, validates the complete certificate chain from the leaf through intermediates to a trusted root CA, and calculates a precise countdown to expiry. This gives you a clear, actionable snapshot of any domain's SSL health in seconds.

The tool is completely free, requires no sign-up, and supports 12 languages. Use the ToolSwitcher pill bar to navigate here from any other Domainwise tool, or arrive with a pre-filled query via the ?q= parameter from RelatedTools suggestion chips.

What the SSL Checker Reveals

Each SSL check on Domainwise returns a comprehensive report covering every critical aspect of the certificate. Here is what you will see in the results:

• Issuer and Subject — Identifies which Certificate Authority (CA) issued the certificate and the organization it was issued to. Extended Validation (EV) and Organization Validated (OV) certificates display verified company details, while Domain Validated (DV) certificates confirm domain ownership only.
• Subject Alternative Names (SANs) — A single certificate can protect multiple domains and subdomains. The SAN list shows every domain name covered, so you can verify that www.example.com, api.example.com, and the apex example.com are all included.
• Validity Period and Days Remaining — The exact start and expiry dates of the certificate are displayed alongside a calculated countdown. This is the most actionable field for certificate management: if days remaining drops below 30, renewal should be a priority.
• Certificate Chain — The checker validates the full chain of trust from the server's leaf certificate through any intermediate CA certificates up to a trusted root. An incomplete chain is one of the most common causes of SSL warnings on certain browsers and devices.
• Protocol Version and Signature Algorithm — See the negotiated TLS version (TLS 1.2 or TLS 1.3) and the signature algorithm (SHA-256 with RSA or ECDSA). Modern security best practice requires TLS 1.2 or higher and SHA-256 or stronger signatures.

After reviewing the certificate, verify the website is online and responding with our Website Status checker.

Common SSL Issues and What They Mean

SSL problems can manifest as browser warnings, connection failures, or certificate issuance errors. Here are the most common issues and how to resolve them:

• Certificate expired — The certificate's validity period has passed. Browsers will display a prominent security warning. Renew the certificate immediately through your CA or hosting provider's certificate management panel.
• Domain mismatch — The certificate's Common Name or SANs do not include the domain being accessed. This often happens when accessing a subdomain that was not included in the original certificate. A new certificate covering all required domains is needed.
• Incomplete certificate chain — The server is not sending one or more intermediate certificates required to build the chain of trust to a root CA. This causes warnings on some browsers and devices but may appear to work on others. Configure your web server to send the full chain bundle.
• Self-signed certificate — The certificate was generated locally and not signed by a trusted CA. Acceptable for internal development and testing environments, but public visitors will see a security warning. Use a trusted CA like Let's Encrypt for production.
• Weak signature algorithm — Older algorithms like SHA-1 are deprecated and considered insecure. Modern browsers may reject or warn about SHA-1 certificates. Ensure your certificate uses SHA-256 or a stronger algorithm.

Check the registration details and ownership of any domain with our DNS Lookup tool to investigate CAA records that control certificate issuance.

SSL vs TLS: Understanding the Terminology

The terms SSL and TLS are often used interchangeably, but they refer to different versions of the same security protocol. SSL (Secure Sockets Layer) was the original protocol developed in the 1990s, while TLS (Transport Layer Security) is its modern successor. All current "SSL certificates" actually use the TLS protocol:

• SSL 2.0 and 3.0 — Deprecated and considered insecure. No modern browser supports them.
• TLS 1.0 and 1.1 — Officially deprecated as of March 2021. Most browsers have removed support.
• TLS 1.2 — Widely supported and considered secure. The minimum acceptable version for production websites.
• TLS 1.3 — The latest version, offering improved security and faster handshakes. Supported by all modern browsers and recommended where possible.

Domainwise reports the negotiated TLS protocol version in the check results, so you can verify that your server supports modern TLS. The tool uses the common term "SSL" for familiarity, but it is checking TLS certificates under the hood.

Related Guides

Learn more about SSL/TLS certificates and web security with this in-depth article from the Domainwise knowledge base:

• SSL Certificates Explained — A full guide covering how SSL/TLS certificates work, the differences between DV, OV, and EV certificates, how the certificate chain of trust operates, and best practices for managing certificates on your domains.

Explore all our free domain tools including WHOIS lookup, DNS record queries, website status monitoring, domain age checking, IP geolocation, Punycode conversion, and social handle checking.