What is a .DER file?
DER is the binary encoding of an X.509 certificate or key.
- Did you know
- DER is the strict binary form of the same X.509 certificates that PEM stores as text.
- DER is defined by the ITU-T X.690 standard as a strict form of ASN.1 that allows exactly one way to encode each value.
- That single-encoding rule is what makes DER suitable for digital signatures, where the bytes must be reproducible.
- What Analyser reads
- Identify and decode X.509 security certificates (CRT, CER, PEM, DER) - subject, issuer, validity dates, and key details.
- Depth of analysis
- .DER 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 .DER file
- Drag a .DER 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 · .CER · .PEM. See all supported file types.