Theo's Typesafe Cult•12mo ago

How to get rid of CORS errors

I keep getting cors error when I tried to connect my front and back end applications. It works on localhost but when I deployed both of them, it just fails. I did some googling and they said I should add this to my app.js

const corsConfig = {
  origin: [
    "https://blog-hed03m1mq-complexlity.vercel.app",
    "http://localhost:3000",
    "https://blog-cms-git-cors-complexlity.vercel.app"
  ],
  credentials: true,
  methods: "GET,HEAD,OPTIONS,PUT,PATCH,POST,DELETE",
  allowedHeaders: ["Content-Type"],
};

app.use(cors(corsConfig));

const corsConfig = {
  origin: [
    "https://blog-hed03m1mq-complexlity.vercel.app",
    "http://localhost:3000",
    "https://blog-cms-git-cors-complexlity.vercel.app"
  ],
  credentials: true,
  methods: "GET,HEAD,OPTIONS,PUT,PATCH,POST,DELETE",
  allowedHeaders: ["Content-Type"],
};

app.use(cors(corsConfig));

Which I did but it still doesn't work Frontend - Nextjs, deploy - vercel Backend - Nodejs/express deploy - railway Frontend code executing the function

   const response = await fetch(url, {
  method: "POST",
  headers: {
    ...headers,
    "Content-Type": "application/json",
  },
      credentials: "include",
  body: JSON.stringify(values)

   const response = await fetch(url, {
  method: "POST",
  headers: {
    ...headers,
    "Content-Type": "application/json",
  },
      credentials: "include",
  body: JSON.stringify(values)

5 Replies

Complexlity•12mo ago

Update: I tried to use render to host the api and till the same thing. I noticed it does not even show the request on the node logs. I pinged /api/v1/sessions (IMAGE 1) but it still doesn't show on the logs (IMAGE 2) could it be the browser?

JulieCezar•12mo ago

try setting origin: "*" with a * to allow all origins... just to see if it works

Complexlity•12mo ago

Okay 👌 . Will do I just remember I tried that. It didn’t work because I have credentials:true. Apparently, to send credentials, you have to put some allowed domains and cannot used *

wlvz•12mo ago

you can change your middleware so that if you hit the api endpoint it will append the headers

export async function middleware(request: NextRequest) {
  const response = NextResponse.next()

  if (request.nextUrl.pathname.startsWith("/api")) {
    response.headers.append("Access-Control-Allow-Origin", "*")
  }
  //...
  return response
}

export async function middleware(request: NextRequest) {
  const response = NextResponse.next()

  if (request.nextUrl.pathname.startsWith("/api")) {
    response.headers.append("Access-Control-Allow-Origin", "*")
  }
  //...
  return response
}

Complexlity•12mo ago

Oh wow. Does that work if you use a different backend server. I use node/express in this case and not the nextjs api route

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How to get rid of CORS errors