What is a .CER file?
CER holds an X.509 security certificate, used to prove identity and secure connections.
- Did you know
- Windows treats .cer as its house extension for certificates - double-clicking one opens the built-in certificate viewer with its Install Certificate button, and the Certificate Export Wizard saves to .cer by default.
- The X.509 certificate standard grew out of the ITU’s X.500 directory work, which aimed to provide a global electronic “white pages”.
- A .cer file may hold the certificate as raw binary DER or as Base64-wrapped PEM text, despite sharing the same extension.
- What Analyser reads
- Identify and decode X.509 security certificates (CRT, CER, PEM, DER) - subject, issuer, validity dates, and key details.
- Depth of analysis
- .CER is an identification-grade format: Analyser recognises it from its bytes and decodes the header metadata it carries, rather than opening it in a full viewer. Formats that do get a full viewer are marked "Full" on the formats page.
- Open a .CER file
- Drag a .CER file onto the Analyser home page (or tap to pick one). It is identified entirely in your browser - nothing is uploaded, there is no account, and it works offline once installed.
- Related formats
- .CRT · .PEM · .DER. See all supported file types.