About Self-Signed Certificate Generator
This free generator makes a self-signed SSL/TLS certificate together with its private key. Enter the domain names or IP addresses, choose the key type and how long the certificate should be valid, and download the .crt and .key files. The certificate includes the SAN extension, server-authentication usage and basic constraints, so modern browsers and servers accept it.
Self-signed certificates are ideal for development, testing, home labs and internal services. Browsers show a warning because no trusted authority signed them, so public websites need a certificate from a trusted authority instead. Everything is generated in your browser and never uploaded.
How to use Self-Signed Certificate Generator
- 01
Enter the domain names or IP addresses.
- 02
Choose the key type and how long it should be valid.
- 03
Download the certificate (.crt) and the private key (.key).
When to use it
- HTTPS on localhost or a development server.
- Internal dashboards, NAS boxes and home-lab services.
- Testing TLS settings before ordering a real certificate.
- Securing traffic between internal services.
- Creating a test .pfx file together with the PFX converter.
Frequently asked questions
Why does my browser warn about a self-signed certificate?
No trusted certificate authority vouches for it. That is fine for testing and internal tools, but not for public websites.
How long can the certificate be valid?
From 30 days to 10 years. Some clients, such as Apple devices, reject server certificates valid for longer than 825 days.
Is the private key uploaded?
No. It is generated in your browser and stored nowhere.