About

What is x509.io?

An open-source tool powered by the @peculiar/certificates-viewer web components. All ASN.1 decoding happens entirely in your browser — certificates never leave your machine.

40+
Extensions supported
3
RFC schemas
100%
Client-side — no server
6
Certificate types
0
Dependencies to install
100% Private
All parsing is done locally. No certificate data is ever sent to a server — safe for sensitive or internal certificates.
Pure JavaScript
Built on asn1-schema for fast, dependency-free ASN.1 decoding. Works offline once loaded.
Embeddable
Framework-agnostic web components. Drop them into React, Vue, Angular, or plain HTML with a single script tag.
Quick Install 
$ npm install @peculiar/certificates-viewer

// or via CDN
<script type="module" src="https://cdn.jsdelivr.net/npm/@peculiar/certificates-viewer/dist/peculiar/peculiar.esm.js"></script>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/@peculiar/certificates-viewer/dist/peculiar/peculiar.css" />

// then drop the component anywhere
<peculiar-certificate-viewer
  certificate="-----BEGIN CERTIFICATE-----...">
</peculiar-certificate-viewer>
Supported

Schemas & Extensions

RFC Schemas
rfc5280
X.509 Certificate & CRL
Internet PKI certificate and revocation list profile
rfc2986
PKCS #10 / CSR
Certification Request Syntax Specification
rfc5755
Attribute Certificate
Attribute Certificate Profile for Authorization
Extensions 40+ supported
Subject Alt Name Key Usage Extended Key Usage Basic Constraints Authority Key ID Subject Key ID CRL Distribution OCSP / AIA Cert Policies Name Constraints CT Precertificate Android Attestation Adobe Timestamp CABF Org ID MS Cert Template Biometric Info Policy Mappings Inhibit AnyPolicy Delta CRL Logo Type LEI TN Auth List + 18 more