<palign="center"><imgwidth="498"alt="Chrome and Firefox screenshot"src="https://user-images.githubusercontent.com/1225294/51066373-96d4aa80-15be-11e9-91e2-f4e44a3a4458.png"></p>
Using certificates from real certificate authorities (CAs) for development can be dangerous or impossible (for hosts like `example.test`, `localhost` or `127.0.0.1`), but self-signed certificates cause trust errors. Managing your own CA is the best solution, but usually involves arcane commands, specialized knowledge and manual steps.
mkcert automatically creates and installs a local CA in the system root store, and generates locally-trusted certificates. mkcert does not automatically configure servers to use the certificates, though, that's up to you.
> **Warning**: the `rootCA-key.pem` file that mkcert automatically generates gives complete power to intercept secure requests from your machine. Do not share it.
To only install the local root CA into a subset of them, you can set the `TRUST_STORES` environment variable to a comma-separated list. Options are: "system", "java" and "nss" (includes Firefox).
For the certificates to be trusted on mobile devices, you will have to install the root CA. It's the `rootCA.pem` file in the folder printed by `mkcert -CAROOT`.
On iOS, you can either use AirDrop, email the CA to yourself, or serve it from an HTTP server. After opening it, you need to [install the profile in Settings > Profile Downloaded](https://github.com/FiloSottile/mkcert/issues/233#issuecomment-690110809) and then [enable full trust in it](https://support.apple.com/en-nz/HT204477).
For Android, you will have to install the CA and then enable user roots in the development build of your app. See [this StackOverflow answer](https://stackoverflow.com/a/22040887/749014).
Node does not use the system root store, so it won't accept mkcert certificates automatically. Instead, you will have to set the [`NODE_EXTRA_CA_CERTS`](https://nodejs.org/api/cli.html#cli_node_extra_ca_certs_file) environment variable.
The CA certificate and its key are stored in an application data folder in the user home. You usually don't have to worry about it, as installation is automated, but the location is printed by `mkcert -CAROOT`.
If you want to manage separate CAs, you can use the environment variable `$CAROOT` to set the folder where mkcert will place and look for the local CA files.
Remember that mkcert is meant for development purposes, not production, so it should not be used on end users' machines, and that you should *not* export or share `rootCA-key.pem`.