X.509 Certificate (PEM) Inspector
X.509 Certificate (PEM) Inspector: Parses ASN.1 DER sequence, decodes X.509 v3 fields, extracts Subject Alternative Names (SAN), and validates dates.
About this x.509 certificate (pem) inspector
X.509 Certificate (PEM) Inspector — browser-based utility.
How this tool works
Implements client-side X.509 Certificate (PEM) Inspector operations. Parses ASN.1 DER sequence, decodes X.509 v3 fields, extracts Subject Alternative Names (SAN), and validates dates specifically designed for a systems administrator inspects an ssl/tls server certificate to check subject, issuer, and san domains.
- PEM Armor Stripping & DER Decoding: Strips '-----BEGIN CERTIFICATE-----' headers and decodes Base64 to raw ASN.1 DER binary bytes.
- ASN.1 Structure Traversal: Parses the TBSCertificate sequence, extracting serial numbers, signature algorithms, and X.500 distinguished names.
- Extension Extraction: Decodes X.509v3 extensions, extracting SAN DNS names, basic constraints (CA flag), and key usage flags.
- Diagnostic Reporting: Computes SHA-256 fingerprint, checks expiration status against the current date, and warns if certificates are expired or self-signed.
Worked example
Scenario: A systems administrator inspects an SSL/TLS server certificate to check subject, issuer, and SAN domains.
Sample input:
Processing: Parses ASN.1 DER sequence, decodes X.509 v3 fields, extracts Subject Alternative Names (SAN), and validates dates.
Illustrative output:
Limits and verification
Rejects corrupted PEM files with invalid Base64 characters or missing encapsulation boundaries. Warns users when inspecting self-signed root certificates or certificates with weak 1024-bit RSA keys.
Examples demonstrate an expected workflow; they do not prove every input or every branch of an external specification. Check important results with an independent source before using them for money, security, compliance, safety, or irreversible file changes.
Browser processing boundary
Tool input is processed by code running in the browser and is not intentionally sent to a CZOA processing API. The page can still request ordinary site assets, analytics, or advertising when those services are enabled. Browser extensions and managed-device software remain outside this tool's control.
Relevant references
These references govern or help explain the format, protocol, or calculation used here. Listing a reference does not claim certification or complete implementation of every optional feature.
Content owner: CZOA Tools · Last reviewed: 2026-09-15 · Review methodology
How to use it
- Enter, paste, or select your input data into the X.509 Certificate (PEM) Inspector workspace controls.
- Review available parameter fields, units, formats, or options configured for your task.
- Click the action button or observe immediate live calculations rendered in your browser runtime.
- Inspect the resulting output and any diagnostic messages, then copy or download the result if needed.
Frequently asked questions
What does X.509 Certificate Inspector parse?+
It attempts to parse the supplied PEM or certificate text and, on success, returns validity, subject, issuer, dates, signature algorithm, extensions, and self-signed status.
What did the browser fixture verify?+
The non-certificate input returned a structured X.509 result with valid false, proving parse failures are represented rather than treated as certificates.
Does valid true prove a certificate is trusted?+
No. It means the input parsed and its reported fields were read. Trust-chain validation, hostname matching, revocation, and current policy are separate checks.
Can it repair a damaged certificate?+
No. It inspects supplied text and returns an error for malformed input. It does not reconstruct PEM, fetch intermediates, or issue certificates.