How it works
Complete the job in three clear steps
- Paste a PEM certificate or chain, or choose a PEM/DER certificate file.
- Inspect the parsed fields and locally calculated results.
- Copy or download the JSON report for review.
Private X.509 certificate tool
Certificate Expiry Checker
Check X.509 not-before and not-after dates locally and report whether each certificate is active, upcoming, or expired.
Free to use Certificate bytes are parsed in this browser and are never sent to Lucaden.
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Important
Check the result before relying on it
Scan-test generated codes before printing or distribution. A generated barcode does not register identifier ownership, and decoded external links should be checked before opening.
Practical details
What this Lucaden tool does
Check X.509 not-before and not-after dates locally and report whether each certificate is active, upcoming, or expired.
Peculiar X.509 supplies standards-aware ASN.1 parsing. Lucaden adds focused reports and makes the limits of offline inspection explicit.
Included capabilities
- Exact UTC validity dates
- Days remaining
- Expired and not-yet-valid states
- Multiple-certificate reports
Useful for
- Review renewal timing
- Audit a PEM bundle
- Check a downloaded certificate
- Document an expiry date
Questions
About this tool
Does this prove a certificate is trusted by my browser?
No. Local parsing and signature checks do not consult an operating-system trust store, hostname policy, revocation service, OCSP, or certificate transparency logs.
Can I inspect a private internal certificate?
Yes. Certificate bytes stay on this device, but avoid pasting a private key because none is needed for these tools.
Open-source foundations
Built transparently
Lucaden documents its standards sources, architectural references, and permissive runtime dependencies while keeping this workspace consistent with the Lucaden interface.