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Express on Netlify

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

# Key features

These features provide important benefits for Express apps, including ones built and deployed with Netlify.

  • Routing. Express provides a robust routing API that allows you to perform complex routing tasks. With this API, you can split code on a per-route basis and not be strictly limited by Netlify’s file-based routing for Functions.
  • Middleware. Express provides a comprehensive set of HTTP utility methods and middleware that you can use to develop a robust API for your application.

# Netlify integration

Express apps on Netlify work because of Netlify Functions.

When you deploy an Express app on Netlify as serverless functions, you get to leverage all of the benefits of running on-demand, server-side code without having to run a dedicated server.

# Deploy an Express app on Netlify

This section demonstrates how to deploy an Express project on Netlify — either alongside a frontend app that uses another framework, or as a standalone Express app.

# Use Express with a frontend app

Before you begin, make sure you have Node.js version 16.0.0 or later installed on your machine. Then, you can start a new project using Express.

  1. Install the following dependencies. If your Express project uses JavaScript, you can exclude @netlify/functions and @types/express.

    npm i express serverless-http @netlify/functions @types/express

  2. Create a Netlify Function file for either TypeScript or JavaScript. For example, you might create a function file called api.ts.

  3. In the newly created file, write the function that will import Express and create a router object to handle routing. Here is an example:

    // YOUR_BASE_DIRECTORY/netlify/functions/api.ts

import express, { Router } from 'express';
import serverless from 'serverless-http';

const api = express();

const router = Router();
router.get('/hello', (req, res) => res.send('Hello World!'));

api.use('/api/', router);

export const handler = serverless(api);

  4. Add the following configuration in your netlify.toml:

    [functions]
  external_node_modules = ["express"]
  node_bundler = "esbuild"
[[redirects]]
  force = true
  from = "/api/*"
  status = 200
  to = "/.netlify/functions/api/:splat"

    In the redirects section is a rewrite that enables Express to parse the URLs configured in your function file. In this example, Express can now successfully parse /api, which we configured above with api.use('/api/', router);.

    If you don’t wish to add the rewrite, you might have to change the configuration in your function to specify the functions path, such as api.use('/.netlify/functions/', router);.

  5. You can now use these routes in your frontend code. In the above example, you can access the /hello route at /api/hello and any other route that you might add at /api/<slug>.

# Use Express without a frontend

It’s possible to deploy Express apps on Netlify without a frontend. If you do this, you can access the routes from other frontend apps deployed separately, just as you would with any other API endpoints. In this case, you might have to configure CORS to allow access to the routes from other domains.

To deploy an Express app without a frontend:

  1. Follow the steps documented above to install Express, create a Netlify Function with your routing code, and create a netlify.toml file to register the function and redirects required.
  2. In the netlify.toml or the Netlify UI, set a placeholder build command to ensure Netlify builds your functions. For example, the command could be echo Building Functions.

# Limitations

  1. Since Express apps are deployed as Netlify Functions, all of the function limitations apply. This includes execution and memory limits.
  2. It is not recommended to deploy Express apps as background or scheduled functions.

# More resources

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