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Security

X.509 Certificate & PEM Inspector

Decode certificates, SANs, key usage, and validity without sending private material away.

Web Worker Local onlyTools
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Certificate evidence dossier · public facts, bounded verdicts

Parsed is not trusted.

A certificate is a signed collection of identity and policy fields. Reading those fields, checking the current time, matching a hostname, and building a trusted path are separate investigations.

PEM

Base64-armored text

-----BEGIN CERTIFICATE-----
DER

Binary ASN.1 bytes

30 82 …

This workbench accepts one public certificate. It never asks for a private key and does not fetch a server or trust store.

X.509 CERTIFICATESERIAL · 04:8D:6A:30:5C:2B:7E:49
SUBJECT
CNapi.example.test
OExample Platform
OUProduction
CUS
ISSUER
CNExample Issuing CA 03
OExample Trust Services
CUS

Validity horizon

The local clock answers one narrow question.

NOT BEFORE

2026-05-12T00:00:00Z

NOW

inside the window

CLOCK
NOT AFTER

2026-08-10T23:59:59Z

FUTURE

now < notBefore

CURRENT WINDOW

notBefore ≤ now ≤ notAfter

EXPIRED

now > notAfter

SAN name map

Identity candidates live in Subject Alternative Name.

The inspector’s wildcard candidate check covers exactly one left-most DNS label. A local match is evidence, not a browser trust decision.

DNS*.example.test
DNSapi.example.test
DNSstatic.example.test
IP192.0.2.24

Key & signature card

PUBLIC KEYEC · P-256
SIGNATUREECDSA with SHA-256
SHA-256 FP8E:2B:4D:9C:…:91:00
SHA-1 FP26:6C:8B:…:48:81 · legacy ID

A fingerprint identifies exact certificate bytes. Trust depends on an authenticated comparison or a validated chain—not the fingerprint label alone.

Extension control panel

BASIC

Basic Constraints · Key Usage · EKU

IDENTITY

SAN · Subject Key ID · Authority Key ID

POLICY

Certificate Policies · Name Constraints

STATUS

AIA / OCSP · CRL Distribution Points

TRANSPARENCY

Signed Certificate Timestamps

01
PARSED

Syntax and ASN.1 structure were decoded

approved
02
TIME

Current clock is inside or outside the stated window

conditional
03
HOSTNAME

Candidate matches a parsed SAN under local rules

conditional
04
CHAIN / REVOCATION

Needs intermediates, trust anchors, policy and fresh status evidence

not asserted

OpenSSL handoff

$ openssl x509 -in cert.pem -noout -text -fingerprint -sha256$ openssl verify -CAfile roots.pem -untrusted chain.pem cert.pem

Direct answer

What is X.509 Certificate & PEM Inspector?

Decode a PEM or DER X.509 certificate locally, inspect subject, issuer, SANs, validity, public key, fingerprints, and extensions without claiming chain or revocation trust.

What can it do?

  • Inspect
  • Hostname

How to use X.509 Certificate & PEM Inspector

  1. 01

    Choose a task

    Select Inspect and Hostname in the workspace.

  2. 02

    Provide the input

    Paste a PEM certificate or open a DER file. The input stays in the browser processing path.

  3. 03

    Review the result

    Run the tool, inspect its result and diagnostics, then copy or download the output when the page offers that action.

Frequently asked questions

What is X.509 Certificate & PEM Inspector?
Decode a PEM or DER X.509 certificate locally, inspect subject, issuer, SANs, validity, public key, fingerprints, and extensions without claiming chain or revocation trust.
What can X.509 Certificate & PEM Inspector do?
X.509 Certificate & PEM Inspector supports Inspect and Hostname. Each mode is available directly in the page workspace.
Does X.509 Certificate & PEM Inspector upload my data?
X.509 Certificate & PEM Inspector processes your input locally in the browser. DevSexy does not add an upload, account, or server-processing step to this workflow.
DevSexy processes tool input locally. No paste tracking, accounts, or upload step.