What is a .CRT file?
CRT holds an X.509 security certificate, used to prove identity and secure HTTPS.
- Did you know
- X.509, the certificate standard behind HTTPS, was first published in 1988.
- The .crt extension is the Unix and Linux convention for certificates, where Apache and Nginx typically expect them.
- Whether a CRT holds text PEM or binary DER is down to its contents, not the extension - the name itself implies neither.
- What Analyser reads
- Identify and decode X.509 security certificates (CRT, CER, PEM, DER) - subject, issuer, validity dates, and key details.
- Depth of analysis
- .CRT 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 .CRT file
- Drag a .CRT 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
- .CER · .PEM · .DER. See all supported file types.