How to link Gatsby.js with my Express server

Add this to your Gatsby-config file

module.exports = {  proxy: {    prefix: "/users",    url: "http://localhost:3000",  },}

This way, when you fetch('/users/todos') in development, the development server will recognize that it’s not a static asset, and will proxy your request to http://localhost:3000/users/todos as a fallback.

In development you need to add to your gatsby-config.js the proxy-middleware as others have said. In production will be totally dependent on where you are running/hosting the Gatsby project.Is your project self-hosted? It depends on what HTTP web server you are running. Nginx for example: you need to open the Nginx configuration file and create a block that allows calls to find your express server on port 3000 (http://nginx.org/en/docs/beginners_guide.html)

location /api {proxy_set_header 'Access-Control-Allow-Origin' 'http://xxx.xxx';proxy_set_header 'Access-Control-Allow-Methods' 'GET, POST, OPTIONS, PUT, DELETE';proxy_set_header 'Access-Control-Allow-Headers' 'X-Requested-With,Accept,Content-Type,Origin';proxy_pass http://127.0.0.1:3000;proxy_redirect off;proxy_buffering on;proxy_set_header    Host                        $host;proxy_set_header    X-Real-IP               $remote_addr;proxy_set_header    X-Forwarded-For $proxy_add_x_forwarded_for;proxy_set_header    origin                  `http://xxx.xxx';}

This example is from https://www.rodrigoplp.com/blog/using-your-own-server-with-gatsby

I had this exact same problem, and solved it by following the advice under "Advanced Proxying" on the GatsbyJS website:

https://www.gatsbyjs.org/docs/api-proxy/#advanced-proxying

My suggestion to you is that you modify your gatsby-config.js (not the package.json) file to the following:

var proxy = require("http-proxy-middleware")module.exports = {  developMiddleware: app => {    app.use(      proxy({        target: "http://localhost:3000",      })    )  },}

You might need to create the gatsby-config.js file. You also might need to remove the "proxy" line from your package.json file.