In the Developer Portal, some extensions have a Base URL field. This indicates that the extension must provide the URL of a server that can receive and respond to HTTP requests from Canva. You can use any programming language, framework, or architecture to handle these requests.

This tutorial explains how to set up a Base URL with:

• ​Express.js - A minimal web framework for Node.js.

• ​ngrok - A free CLI that exposes a local server via a publicly accessible URL.

Step 1: Install Node.js

To check if Node.js is installed, run the following command:

node --version

You should see something like this:

$ node --version
v14.15.0

If it's not installed, download it from the official website.

Step 2: Set up a new project

Create a project with the following structure:

• my-app

  • src/

    • server.js

  • .env

  • package.json

To create this structure, run the following commands:

mkdir my-app
cd my-app
npm init --yes # yarn init
mkdir src
touch .env src/server.js

Then copy the following code into the server.js file:

require('dotenv').config();
const express = require('express');
​
const app = express();
​
app.use(express.json());
app.use(express.static('public'));
​
// Routes go here
​
app.listen(process.env.PORT || 3000);

This code initializes an Express.js server without any endpoints. The required endpoints depend on the app's extensions and how they're configured.

Step 3: Install the dependencies

Install the following runtime dependencies:

• ​express​

• ​dotenv​

• ​nodemon​

To install these dependencies, run the following command:

npm install express dotenv --save && npm install nodemon --save-dev
# yarn add express dotenv && yarn add nodemon --dev

Step 4: Start the local server

Copy the following script into the package.json file:

"scripts": {
  "start": "nodemon src/server.js"
}

Then start the local server with the start command:

npm run start
# yarn start

The local server becomes available at http://localhost:3000.

Step 5: Expose the local server

For Canva to send requests to a local server, it needs to be exposed via a publicly available URL. One of the easiest ways to do this is with ngrok.

ngrok is a free tool that creates a secure tunnel to a local server. You can create tunnels without an account, but the tunnels expire after a few hours of activity. If you have an account, the tunnels don't expire.

To install ngrok, run the following command:

npm install ngrok --global

To verify that ngrok is installed, run the following command:

ngrok version

You should see something like this:

$ ngrok version
ngrok version 2.3.35

If you run into any errors, refer to the official installation instructions.

To start an ngrok tunnel, run the following command in a separate terminal while the local server is still running:

ngrok http 3000

This command assumes the port of the local server is 3000.

After running this command, ngrok provides a HTTPS-enabled URL that can receive requests from Canva. You can enter this URL into the extension's Base URL field.

Example

src/server.js

require('dotenv').config();
const express = require('express');
​
const app = express();
​
app.use(express.json());
app.use(express.static('public'));
​
// Routes go here
​
app.listen(process.env.PORT || 3000);

.env

# add environment variables here

package.json

{
  "name": "my-app",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "start": "nodemon src/server.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "dotenv": "^8.2.0",
    "express": "^4.17.1"
  },
  "devDependencies": {
    "nodemon": "^2.0.6"
  }
}