SSL Certificate Decoder — Parse PEM X.509
Paste PEM certificate to read subject, issuer, SAN, validity, and serial
How to Use This Tool
- Paste full PEM certificate text into textarea.
- decodePem library parses base64 body client-side.
- Valid parse populates type, subject, issuer, dates, serial, SAN list.
- Copy JSON summary of key fields.
- Invalid input shows parse error message.
About This Tool
VSPIC SSL certificate decoder parses PEM-encoded X.509 certificates client-side, extracting subject distinguished name, issuer, validity notBefore and notAfter, serial number, and subject alternative names when present in certificate text.
Paste between BEGIN CERTIFICATE and END CERTIFICATE markers. Invalid PEM shows error without sending material to servers — suitable for auditing certs from confidential infrastructure.
Common use cases
- •Inspect HTTP headers and user-agent strings
- •Analyze email headers for phishing investigation
- •Generate strong passwords for staging environments
PEM format basics
Privacy Enhanced Mail wrapper base64 encodes DER certificate with header footer lines — standard export from OpenSSL and certificate authorities.
Subject and issuer DN
Subject identifies certificate holder — CN common name, O organization, C country. Issuer identifies signing CA — chain validation walks issuer to trusted root.
Subject Alternative Names
SAN extension lists additional hostnames and IPs valid for TLS — modern HTTPS relies on SAN more than CN alone.
Validity period audit
notBefore and notAfter bound acceptable TLS usage — compare notAfter with calendar before outages from expired certs.
Serial number tracking
Serial hex identifies cert instance for revocation list correlation and inventory databases.
Client-side privacy
Private keys not accepted here — certificate decoder tool rejects or ignores key material; never paste PRIVATE KEY blocks into untrusted sites regardless.
Limitations versus OpenSSL
Deep extension parsing may be partial — use openssl x509 for full ASN.1 dump when debugging exotic extensions.
Relationship to ssl-checker
Live ssl-checker fetches chain from host. Decoder inspects PEM you already downloaded offline.
CSR distinction
Certificate decoder expects issued cert. CSR decoder handles certificate signing requests separately.
Compliance documentation
Export decoded JSON fields into asset inventory proving cert ownership and expiry tracking.
Frequently Asked Questions
Yes. VSPIC offers this SSL certificate decoder at no cost with no account required. Results load in real time.
We do not permanently store your queries on our servers. Some tools run entirely in your browser; others fetch public data for the request only.
Yes. Open the page in any modern phone or tablet browser. Results work on Wi‑Fi and mobile data.
Paste certificate only — not private key PEM blocks.
Client-side parse only.
Paste one cert at a time — chain requires multiple pastes.
Convert to PEM base64 first — tool expects PEM text.
Shown in subject or SAN depending on issuance policy.
Parses same — issuer equals subject pattern visible.
Next step for your check
Continue with csr decoder on VSPIC.
Related Tools
Explore more free VSPIC tools for IP, DNS, security, and network diagnostics.
CSR Decoder
Decode CSR contents, domains, and key details
Use Free →SSL Checker
Validate SSL/TLS certificates and expiration dates
Use Free →SSL/TLS Grade Checker
SSL grade, protocol support, cipher analysis, and expiry
Use Free →Header Checker
Inspect HTTP request and response headers
Use Free →Link Checker
Verify if a URL is reachable and check HTTP status
Use Free →ASN Lookup
Find autonomous system number, name, and network prefix
Use Free →
Trusted by Users Who Value Privacy
Always Free
No premium plan ever
100% Private
Files processed in browser
Instant Results
Convert in seconds
Works Everywhere
Any device, any OS