Self-Signed Certificate Generator — Free Online SSL Cert Generator
Generate a self-signed X.509 certificate and RSA private key for localhost, development, and internal HTTPS — 100% in-browser.
Frequently Asked Questions
Self-Signed Certificates for Development and Internal Use
A self-signed SSL certificate is a certificate that is signed by its own private key instead of a trusted third-party Certificate Authority. Browsers will show a warning when a self-signed certificate is encountered on a public site, but they are fully functional for internal networks, local development, and server-to-server communication.
Common use cases: localhost HTTPS for local development (React, Vue, Node.js dev servers), Docker containers communicating with mutual TLS, Kubernetes internal services, staging environments, CI/CD pipelines, and testing SSL configuration before purchasing a certificate.
This generator creates an RSA key pair and X.509 v3 certificate with Subject Alternative Names (SANs), key usage, and extended key usage extensions. The certificate is signed with SHA-256, which is required by modern browsers (SHA-1 certificates are rejected).
For production websites, use a free Let's Encrypt certificate instead of a self-signed one. Let's Encrypt provides trusted certificates that do not trigger browser warnings.