Enabling Https for local Spring Boot development with mkcert

Today, I discovered mkcert – a tool that generates valid TLS certificate. It works for any hostname or IP, including localhost. In this post, I will show you how to generate a valid PKCS12 format certificate using mkcert. Then, we will use that certificate in a Spring boot application.

We will start by installing mkcert on our local machine. If you are using Mac then we can use brew package manager. For installation instructions specific to your OS you can refer to the documentation.

brew install mkcert

Once mkcert is installed, you can use its CLI to create and install a CA. To do that, run the following command.

mkcert -install

Using the local CA at "/Users/shekhargulati/Library/Application Support/mkcert" ✨
The local CA is now installed in the system trust store! ⚡️
The local CA is now installed in Java's trust store! ☕️

As you can see from the above output, it created and installed CA in both my system and Java’s trust store.

For Java, it is required that JAVA_HOME environment variable is set.

Once CA is created and installed, we can create the PKCS12 format certificate. Java supports two certificate formats:

  1. PKCS12: Public Key Cryptographic Standards is a password protected format that can contain multiple certificates and keys; it’s an industry-wide used format
  2. JKS: Java KeyStore is similar to PKCS12; it’s a proprietary format and is limited to the Java environment.

mkcert support PKCS12 format only.

To generate the PKCS12 certificate, we will use the following command.

mkcert -pkcs12 localhost

The output of the above command is shown below.

Using the local CA at "/Users/shekhargulati/Library/Application Support/mkcert" ✨

Created a new certificate valid for the following names 📜
 - "localhost"

The PKCS#12 bundle is at "./localhost.p12" ✅

The legacy PKCS#12 encryption password is the often hardcoded default "changeit"

It will create the certificate in the current directory. The key store password will be changeit

Now, that we have valid certificate, let’s create the Spring Boot application.

curl https://start.spring.io/starter.zip -d dependencies=web \
           -d bootVersion=2.1.2.RELEASE -o ssl-boot-app.zip

Next, unzip the app

unzip ssl-boot-app.zip && cd ssl-boot-app.zip

Copy the localhost.p12 certificate to src/main/resources directory.

Next, we will set SSL properties in the application.properties file.


Create index.html in the src/main/resources/static directory

<!DOCTYPE html>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Hello, HTTPS</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <h1>Hello, Https!</h1>


Now, you can start the app using the following Maven command.

 mvnw spring-boot:run

The applictation will be running at https://localhost:8443/


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