Need to read who issued a certificate or when it expires? This page turns a DER certificate into structured JSON you can search, copy, or feed into other tools.
How to convert a DER file
- Upload a DER-encoded X.509 certificate file up to 5 MB.
- Press Convert file and review the JSON output.
What you get
A JSON object with subject, issuer, validity window, serial number, public key type, extensions, and other fields from the certificate.
When this helps
- Checking expiry dates before deploying TLS certificates
- Auditing certificate metadata during security reviews
- Extracting subject or SAN details without opening a desktop tool
- Feeding certificate fields into scripts or documentation