Offline certificate inspector

What it does

Inspect the subject, issuer, names, validity dates and SHA-256 fingerprint of a local public certificate.

How to use it

1. Choose one public PEM or DER certificate and a reference date.
2. Inspect fields and download the JSON report. A valid date interval does not establish trust.
3. Processing stays in your browser. No upload or sign-up.

Example

Choose a PEM certificate and a reference date to see whether that date is inside its validity interval.

Methodology

ASN.1 and PKI.js parse one DER or PEM certificate in a worker; Web Crypto computes its SHA-256 fingerprint.

Limitations

One certificate up to 1 MiB. Private keys are rejected. No signature, chain, trust-store or revocation verification; no network requests to issuers. Reference dates use midnight UTC.

Automation

This tool runs in your browser. No upload API or MCP endpoint is available.