What are Subject Alternative Names (SANs)?

SANs allow a single SSL certificate to secure multiple domain names, subdomains, and IP addresses.

Updated: August 2026 • Verified v1.2

SSL / TLS X.509 Certificate Decoder & Inspector

Internet & NetworkNetwork

Local Browser Execution: Your input is processed locally in your browser and is not sent to UTL servers.

X.509 Parser: ASN.1 / PEM Decoder ➔ Subject, Issuer, Validity Dates, SANs

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Understanding Your Results

Parses PEM certificate strings, displays Common Name, CA issuer, public key type, signature algorithm, serial number, and remaining expiration days with color-coded status.

Practical Guidance & Next Steps

Never paste private keys (`-----BEGIN PRIVATE KEY-----`). Only paste public certificates (`-----BEGIN CERTIFICATE-----`).

What is this?

A networking security utility that decodes PEM-encoded public X.509 SSL/TLS certificates in browser memory.

How does it work?

1. Paste your PEM certificate (`-----BEGIN CERTIFICATE-----...`). 2. View decoded attributes (Common Name, Issuer, SANs, Validity Dates, Expiration Days). 3. Copy the certificate summary in 1 click.

Why use it?

Quickly verifies certificate attributes without needing local OpenSSL CLI tools.

Technical Scope & Calculation Limitations

Parses standard PEM-encoded X.509 public certificates.

Frequently Asked Questions

Yes. This tool runs 100% client-side in your browser. Furthermore, public certificates contain only public information and do not expose private keys.

Windows Desktop & Widget Options