# Custom certificates By default, Stormkit uses LetsEncrypt to issue certificates automatically. If you want to change this behaviour for specific domains, you can configure custom certificates. To do so: - Visit your **Application** > **Environment** > **Custom Domains** page and locate the domain that you'd like to use a custom certificate. - Locate the `Expand (...)` button and click on that. - Click on **Custom certificate**. - Provide both the `Certificate` and `Private key` that is used while creating the certificate. **Note** Stormkit accepts only PEM encoded files. ## CRT files If you have a certificate with a `.crt` extension, you can use `openssl` to convert it into PEM format: ``` openssl x509 -in example_org.crt -out example_org.pem -outform PEM ```