Understand how SSL and TLS encrypt Internet traffic and keep your data secure.
An SSL certificate is a digital identity card for a website. It proves that a website really belongs to the organization operating it and allows browsers to create an encrypted connection. Although people still say SSL, virtually every modern website actually uses TLS (Transport Layer Security), the successor to SSL.
When you visit a website using HTTPS, everything sent between your browser and the server is encrypted. Without HTTPS, anyone on the same network could potentially view information such as:
Every SSL certificate contains important information, including:
| Field | Description |
|---|---|
| Common Name (CN) | The hostname the certificate protects. |
| Issuer | The Certificate Authority that issued the certificate. |
| Valid From | The date the certificate becomes valid. |
| Expires | The certificate expiration date. |
| Public Key | Used during encryption and authentication. |
| Subject Alternative Names (SAN) | Additional domains covered by the certificate. |
A Certificate Authority (CA) is a trusted organization that verifies website ownership and issues SSL certificates. Some of the most common Certificate Authorities include:
When an SSL certificate expires, browsers begin displaying security warnings. Visitors may see messages such as:
Expired certificates can reduce user trust, interrupt API communications, and prevent users from accessing a website.
| Problem | Description |
|---|---|
| Expired Certificate | The certificate is no longer valid. |
| Hostname Mismatch | The certificate doesn't match the website name. |
| Untrusted Certificate | The issuing CA isn't trusted by the browser. |
| Incomplete Chain | Intermediate certificates are missing. |
| Self-Signed Certificate | The certificate wasn't issued by a trusted CA. |
Use our free SSL Certificate Checker to instantly view:
Want to inspect a live certificate? Use our SSL Certificate Checker to view certificate details, issuer information, expiration dates, and remaining validity.