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HTTPS & Subdomains

Since we’re going to start using cross-subdomain authentication it’s pretty important that we can test both https://app.cal.localhost and https://cal.localhost locally. This is a quick guide on how can we achieve this setup locally for development purposes.

Prerequisites

  • Caddy Server
  • Dnsmasq

Install Dnsmasq

brew install dnsmasq

Configure Dnsmasq to resolve *.localhost domains

First let’s check where our brew installation config files are:
$ brew --prefix
/opt/homebrew
In my case it lives at /opt/homebrew/etc/dnsmasq.conf
# Route all *.localhost addresses to localhost
address=/localhost/127.0.0.1
​
# Don't read /etc/resolv.conf or any other configuration files.
no-resolv
​
# Never forward plain names (without a dot or domain part)
domain-needed
​
# Never forward addresses in the non-routed address spaces.
bogus-priv

Run Dnsmasq now and anytime we restart the system

sudo brew services start dnsmasq

Make macOS use our local DNS server (Dnsmasq) for .localhost addresses

Create the following file at /etc/resolver/localhost:
nameserver 127.0.0.1
With that, you can go to subdomain.localhost in your browser and it will point to localhost. So if your app is running on port 3000, simply go to subdomain.localhost:3000.
But what if you're looking for the following setup?
cal.localhost -> localhost:3001
app.cal.localhost -> localhost:3000
This we can solve with Caddy which is a super-awesome simple HTTP server!

Install Caddy

brew install caddy

Configure Caddy

In my case (because my brew --prefix is /opt/homebrew), my global Caddyfile is at /opt/homebrew/etc/Caddyfile. This file we can setup to act as a simple reverse proxy for our individual apps running on different ports:
https://cal.localhost {
reverse_proxy localhost:3001
}
​
https://app.cal.localhost {
reverse_proxy localhost:3000
}

Run Caddy now and every time your system restarts

brew services start caddy
That's it! If you change your Caddyfile, you will need to brew services restart caddy.

Setup our your environment variables

NEXTAUTH_URL='https://app.cal.localhost'
NEXT_PUBLIC_WEBAPP_URL='https://app.cal.localhost'
NEXT_PUBLIC_WEBSITE_URL='https://cal.localhost'
NODE_TLS_REJECT_UNAUTHORIZED=0 # Needed so HTTPS doesn't complain locally

Run website and web app at the same time

yarn turbo run dev --scope="@calcom/web" --scope="@calcom/website"

Go to the website or web app domain

You should be able to go to https://app.cal.localhost and https://cal.localhost successfully 🙌
Thanks to Max 's article Local subdomains on macOS with Dnsmasq and Caddy for making it easy to get started with Dnsmasq.