Accessing your local Next.js dev server using HTTPS

Miguel Oller

Miguel Oller

July 7, 2022

This post is a step-by-step guide to accessing a Next.js local dev server via HTTPS (e.g., https://localhost:3000).



We will be using `create-next-app` to get a simple Next.js app set up, `mkcert` to generate a locally-trusted SSL certificate, and `local-ssl-proxy` to access our Next.js app’s local dev server via HTTPS.

Running a Next.js app locally and accessing it with HTTP

The easiest way to get started with Next.js is by using `create-next-app`. Let’s create a Next.js app in the `next-https` directory:

npx create-next-app next-https

Once that’s done we can change our working directory and start our local dev server:

cd next-https

yarn dev

We should have a Next.js app running locally which we can access at http://localhost:3000. If we try to access it using HTTPS at https://localhost:3000, though, we’ll get an SSL error. Here’s what I see when trying to open that URL in Google Chrome:

Browser loading error scren

Let’s fix that!

Creating a locally-trusted SSL certificate

To use HTTPS to access our local dev server, we’ll need a locally-trusted SSL certificate.



So what does “locally-trusted” mean?



In very simple terms, when a browser attempts to establish an HTTPS connection with a server, it will request an SSL certificate from the server, check if the certificate has been signed by a trusted Certificate Authority (CA), and if so, establish the connection.



So how does the browser know which CAs to trust? Your operating system keeps a list of trusted CAs in a “trust store”.



If you’re on macOS, the following command will list all the certificates of the CAs trusted by the system, hence the `-s` flag.

security dump-trust-settings -s

These are the first 20 lines I see on my macOS device when I run that command:

Number of trusted certs = 158

Cert 0: Go Daddy Root Certificate Authority - G2

Number of trust settings : 0

Cert 1: HARICA TLS ECC Root CA 2021

Number of trust settings : 0

Cert 2: SwissSign Platinum CA - G2

Number of trust settings : 0

Cert 3: Global Chambersign Root

Number of trust settings : 0

Cert 4: OISTE WISeKey Global Root GA CA

Number of trust settings : 0

Cert 5: KISA RootCA 1

Number of trust settings : 0

Cert 6: Actalis Authentication Root CA

Number of trust settings : 0

Cert 7: D-TRUST Root CA 3 2013

Number of trust settings : 0

Cert 8: Apple Root CA - G2

Number of trust settings : 0

Cert 9: StartCom Certification Authority G2What “locally-trusted” means is that we’ve added a CA to the system’s trust store so that our browsers will accept certificates signed by it. Browsers running on other machines won’t trust this CA which is why it’s “local”.



We can run `dump-trust-settings` again but this time with the `-d` flag to display trusted admin certificates, as opposed to system trusted certificates with `-s`.

What “locally-trusted” means is that we’ve added a CA to the system’s trust store so that our browsers will accept certificates signed by it. Browsers running on other machines won’t trust this CA which is why it’s “local”.



We can run `dump-trust-settings` again but this time with the `-d` flag to display trusted admin certificates, as opposed to system trusted certificates with `-s`.

security dump-trust-settings -s

On my macOS device I see the following output:

SecTrustSettingsCopyCertificates: No Trust Settings were found.

So how do we create a locally-trusted CA and install it into our system’s trust store? For this post, we’ll be using `mkcert`.



`mkcert` is a tool that makes it very easy to make locally-trusted certs for use in development. It is not intended for production use and is optimized for simplicity and zero-configuration. This makes it perfect for our use case and saves us from wrangling with other more comprehensive, production-grade, and necessarily complicated tools, like OpenSSL.



We’ll start by installing `mkcert`. On macOS, you can install `mkcert` using Homebrew.

brew install mkcert

brew install nss # if you use Firefox

For more details regarding installation, including how to install in Linux and Windows, check the `mkcert` README.

Now that we’ve got `mkcert` installed, we’ll create a CA and add it to the local list of trusted CAs. Note that you might be asked for your password so that `mkcert` can modify the system trust store.

mkcert -install

After running that command `mkcert` should have created a CA and added its certificate to the system’s trust store. If you’re following along on macOS, we can verify that by running `dump-trust-settings` again.

security dump-trust-settings -d

This is the output I get now:

Number of trusted certs = 1

Cert 0: mkcert miguel@Miguels-MBP.attlocal.net (Miguel Oller)

Number of trust settings : 0

Now we’re ready to create our SSL cert. All we have to do is run `mkcert` with the desired hostname:

mkcert localhost

This should result in two files being created in the current working directory. The certificate, `localhost.pem` and the key, `localhost-key.pem`.



The `.gitignore` file generated by `create-next-app` ignores `.pem` files so no need to worry about it being checked in to version control.



We can now use this SSL certificate to access our Next.js app via HTTPS!

Accessing the Next.js app locally with HTTPS

So how do we use our certificate with our Next.js development server? Next.js doesn’t support adding an SSL certificate to the development server, so we’ll need something other than Next.js to help us out here.



What we’ll do is run an HTTPS server that will proxy all requests to our Next.js development server. The `local-ssl-proxy` NPM package makes this a breeze.



With our Next.js app running on `localhost:3000`, run the following command in a separate terminal:

npx local-ssl-proxy \

--key localhost-key.pem \ # our encryption key

--cert localhost.pem \ # our certificate

--source 3001 \ # the port we want the proxy server to listen to

--target 3000 # the port our Next.js app is listening on

This will proxy HTTPS traffic from `localhost:3001` to `localhost:3000` as HTTP. `local-ssl-proxy` is acting as an “SSL termination proxy”.



And that’s it! You should be able to visit `https://localhost:3001` and access your Next.js app via HTTPS.



If you’re planning on doing this often it might be worth installing `local-ssl-proxy` as a development dependency and adding a package.json script to start the HTTPS server. Also, if you want to use different ports, the Next.js CLI provides options to override the default port.

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