Self-Signed Certificate Generator

What is a Self-Signed Certificate Generator?

Generate self-signed X.509 TLS/SSL certificates (`.crt) and matching <a href="https://en.wikipedia.org/wiki/RSA_(cryptosystem)" target="_blank" rel="noopener noreferrer" class="text-indigo-600 dark:text-indigo-400 font-semibold hover:underline" title="Learn more about RSA on official docs">RSA</a> private keys (.key`) for local development web servers (`localhost`, `127.0.0.1`, dev domains).

Why Use This Tool?

  • Local HTTPS Web Development: Test HTTPS server configurations, Service Workers, and Secure Cookies on `localhost`.
  • Docker & Kubernetes Staging: Generate self-signed TLS certificates for local container ingress controllers.
  • Instant Development Certificates: Create valid SSL certificates in seconds without installing OpenSSL CLI.

How to Use

  1. Enter Domain Name / SANs (e.g. `localhost`, `127.0.0.1`, `dev.local`).
  2. Select Validity Days (e.g. `365` days) and Key Size (2048 or 4096 bits).
  3. Click Generate and download `.crt` certificate and `.key` private key.

Real Working Example

Input:

Domains (SANs): localhost, 127.0.0.1 | Validity: 365 Days | Key Size: 2048 bits

Output Result:

Certificate (server.crt):
-----BEGIN CERTIFICATE-----
MIIF...

Private Key (server.key):
-----BEGIN PRIVATE KEY-----
MIIE...

Important Technical Details & Security Standards

  • X.509 v3 Certificate Generation Engine: Generates valid X.509 v3 certificates with Subject Alternative Name (SAN) extension fields.
  • SHA-256 Signature Hash: Signs certificate with RSA-SHA256 signature algorithm.
  • 100% Local Generation: Private keys and certificates are generated locally in browser memory.

Related Security & Crypto Tools

Frequently Asked Questions

What is a self-signed SSL certificate?

A self-signed certificate is an X.509 certificate signed by its own creator rather than a publicly trusted Certificate Authority (like Let's Encrypt).

Why does my browser show a "Not Secure" warning for self-signed certificates?

Browsers do not trust self-signed certificates by default because they are not signed by a recognized root CA; you can bypass the warning for local dev.

Can I use self-signed certificates in production?

No, self-signed certificates should only be used for local development and internal testing; use public CAs for production websites.

Is it free?

Yes, 100% free.

Are generated private keys uploaded to a server?

No, certificate and key generation happens 100% locally in your web browser.

Does it support IP addresses like 127.0.0.1 in SAN fields?

Yes, IP addresses and domain names are added to the Subject Alternative Name (SAN) extension.

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