If you have any project questions, concerns, or contribution ideas, join our #pwa Slack channel. Find out how to create an account by visiting Community Resources

Reference Implementation

The upward-js package is a reference implementation of the UPWARD specification built using JavaScript. This package is able to run as standalone server or as an Express/Connect middleware.

If you followed the instructions for Setting up Venia, it automatically sets up and uses this implementation as its application shell server.


Use the following command to install upward-js in your project:

yarn add @magento/upward-js


Use the command line, server API, or middleware API to launch the upward-js server.

Command line

You can make this project available to the command line by installing it globally:

yarn global add @magento/upward-js

Launch the server in the foreground using the following command:


This command does not take arguments. Instead, it uses the following environment variables for configuration:

Variable Required Description
UPWARD_JS_UPWARD_PATH Yes The path to the server definition file.
UPWARD_JS_BIND_LOCAL Yes This must be set to 1.
UPWARD_JS_LOG_URL No Prints the bound URL to stdout if set to 1.

Server API

Require server from @magento/upward-js in your Node script to import the server into your project.


const { server } = require('@magento/upward-js');

const { app } = upward({
  upwardPath: './my-upward-server.yml'


Middleware API

Use middleware from @magento/upward-js to use the middleware into your project. This middleware is compatible with Express 4, Connect, and other frameworks that use this common pattern. It returns a Promise for a function which handles request/response pairs.


const express = require('express');
const { middleware } = require('@magento/upward-js');

const app = express();



You can also pass an IOAdapter as a second argument to the middleware.