Enabling CORS Middleware In Firebase Cloud Functions

Last updated: May 6, 2017

Firebase Cloud Functions are great, but there might come a time where you need CORS support. This can be enabled easily by using the CORS middleware.

The documentation does detail part of the process, but it doesn’t mention you need to install the cors package and also specify origin: true as a configuration option. If you’re new to Node.js, this might catch you off guard.

Go into your functions directory in your application and in your terminal: npm install cors --save this will add the CORS middleware package to your package.json.

Open up your index.js file in the functions directory and add in the following:

const cors = require('cors')({
  origin: true

exports.helloWorld = functions.https.onRequest((req, res) => {
    cors((req, res, () => {
        response.send("Hello from Firebase!");

Notice how we use the CORS middleware function inside of our request handler? You’ve just added in CORS.

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