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Glossary Security

Digital certificate

A digital certificate is a signed file that links a public key to an identity, such as a domain name, so others can trust that key.

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In more detail

Website certificates (X.509) list the domain names they cover, the issuer, the validity dates and the public key, and are signed by a certificate authority that browsers trust, often through a chain of intermediate certificates. Expired, mismatched or untrusted certificates trigger browser warnings.

Try these tools

SSL Certificate Checker

Check any domain's SSL/TLS certificate details server-side — issuer, subject, expiry date, and SAN list.

Certificate Decoder

Decode X.509 certificates and certificate signing requests (CSRs) in your browser: subject, issuer, validity, serial, public key.

See also

  • Glossary TLS
    TLS (Transport Layer Security) is the cryptographic protocol that encrypts and authenticates connections, including HTTPS, email and VPNs.
  • Glossary Public-key cryptography
    Public-key (asymmetric) cryptography uses a pair of linked keys: a public key anyone can have, and a private key kept secret.
  • Glossary Digital signature
    A digital signature is a value computed from a message and a private key that proves who created it and that it has not been changed.
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