NOTE: WebGL performs a lot better with a Reverse Proxy, and that's generally easier to set up and maintain than using cert.json and PFX files.

Go to the Reverse Proxy page for instructions.

If you host your webgl build on a HTTPS domain you will need to use the secure web socket protocol (wss://). WSS requires a SSL certificate set up on your Mirror game server for basic scenarios or on your gateway server for "reverse proxy" scenarios. You will also have to ensure the "Client Use WSS" option is set on the transport.

For the following sections we will demonstrate how to obtain SSL certificates using Let's Encrypt for the domain


  • You need a domain name and the ability to edit DNS records

    • A DNS record should point to your webgl game client (normally hosted on port 443)

    • A DNS record should point to your Mirror game server

  • Set up virtual machine in the cloud: How to set up a Google cloud server

NOTE: you may need to open port 80 for certbot operations.

Get Cert

Follows guides here:

Find the instructions for your server version. Below is link for Ubuntu 18.04 LTS (bionic)

For instruction 7

sudo certbot certonly --standalone

After filling in details you will get a result like this

 - Congratulations! Your certificate and chain have been saved at:
   Your key file has been saved at:
   Your cert will expire on 2021-01-07. To obtain a new or tweaked
   version of this certificate in the future, simply run certbot
   again. To non-interactively renew *all* of your certificates, run
   "certbot renew"
 - If you like Certbot, please consider supporting our work by:

   Donating to ISRG / Let's Encrypt:
   Donating to EFF:           should be your domain

Create cert.pfx

To create a pfx file that SimpleWebTransport can use run this command in the /etc/letsencrypt/live/ folder

openssl pkcs12 -export -out cert.pfx -inkey privkey.pem -in cert.pem -certfile chain.pem

You will be asked for a password; you can set a password or leave it blank. You might need to be superuser in order to do this.


cd /etc/letsencrypt/live/

Note: Currently the mono version shipped with unity is unable to load pfx files generated by OpenSSL version 3. You will have to add the -legacy command line argument to the openssl command above to generate a compatible pfx file.

Using cert.pfx

You can either copy the cert.pfx file to your server folder or create a symbolic link.

Using Move

mv /etc/letsencrypt/live/ ~/path/to/server/cert.pfx

Using Symbolic link

ln -s /etc/letsencrypt/live/ ~/path/to/server/cert.pfx

Create cert.json file

Create a cert.json that SimpleWebTransport can read

Run this command in the ~/path/to/server/ folder

If you left the password blank at cert creation:

echo '{ "path":"./cert.pfx", "password": "" }' > cert.json

If you set up a password "yourPassword" at cert creation:

echo '{ "path":"./cert.pfx", "password": "yourPassword" }' > cert.json

Run your server

After the cert.json and cert.pfx are in the game server folder like this

|- demo_server.x86_64
|- cert.json
|- cert.pfx

Then make the server file executable

chmod +x demo_server.x86_64

To run in the active terminal use


To run in background use

./demo_server.x86_64 &

To keep the game server running even after you close your ssh session use

nohup ./demo_server.x86_64 &

nohup means: the executable will keep running after you close your ssh session the & sign means: that your server will run in background

you may need to use sudo to run if you created a symbolic link

Connect to your game

Test everything is working by connecting a game client to the game server using either the unity editor as a game client or using your deployed webgl build as the game client.

Set your domain (eg in the hostname field and then start a client.

Debugging SSL

To check if your pfx file is working outside of unity you can use pfxTestServer.js (src).

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