Is the private key sent to a server?

No. RSA key generation and signing are all handled by the browser's Web Crypto API, and the generated output follows the same logic that has been verified with actual openssl signature verification.

Can I use this in production?

A self-signed certificate isn't signed by a trusted Certificate Authority (CA), so visitors' browsers will show a warning. For production, use a certificate from a public CA such as Let's Encrypt.

Can I use the generated certificate on a local dev server?

Yes. If you set a local domain such as localhost as the Common Name, you can use it directly with a local HTTPS dev server.

Is the browser warning abnormal?

It is expected — the cert is not from a trusted CA. Proceed via Advanced → continue for testing.

Can it serve a real site?

Not recommended. Use a free CA certificate like Let's Encrypt for public services.

🪄 Self-Signed SSL Certificate Generator

Generate a self-signed SSL certificate and RSA private key for use in testing and development environments.

⚠️ A self-signed certificate isn't issued by a trusted CA, so browsers will show a "not secure" warning. Use it only for local development and testing.

Common Name (domain)

Organization (optional)

Country Code Validity (days) Key Size

How to use

Enter the Common Name (domain) and organization info.
Choose the validity period and key size.
Click "Generate" to download the certificate and private key.

🎯 Use Cases

Enable HTTPS on a local dev server — issue a self-signed certificate for localhost
Set up an internal test environment — build a temporary SSL setup without a public CA
Learn and practice SSL configuration — understand certificate structure and installation

Example

Input

Common Name: localhost
Country: KR   Validity: 365 days   Key Size: 2048 bit

Output

Setting the Common Name to localhost produces a self-signed certificate (cert.pem) whose subject and issuer match, plus a private key (key.pem). Each generation uses a fresh random key, so the actual value differs every time; the output above is a representative sample.

What self-signed certificates are

A self-signed certificate is issued by yourself with no CA — for dev and testing only.

Item	Details
Issuer = subject	No signing CA — outside the browser trust chain
Generated parts	An RSA key pair — certificate (public) and key (private) files
Good for	Local development, internal testing, staging
Not for	Public services — visitors see a security warning

FAQ

Is the private key sent to a server?: No. RSA key generation and signing are all handled by the browser's Web Crypto API, and the generated output follows the same logic that has been verified with actual openssl signature verification.
Can I use this in production?: A self-signed certificate isn't signed by a trusted Certificate Authority (CA), so visitors' browsers will show a warning. For production, use a certificate from a public CA such as Let's Encrypt.
Can I use the generated certificate on a local dev server?: Yes. If you set a local domain such as localhost as the Common Name, you can use it directly with a local HTTPS dev server.
Is the browser warning abnormal?: It is expected — the cert is not from a trusted CA. Proceed via Advanced → continue for testing.
Can it serve a real site?: Not recommended. Use a free CA certificate like Let's Encrypt for public services.