Kevin Powell - Community•3mo ago

How to fix CORS error in Next.js?

export async function POST(req: NextRequest) {
  // req.headers.set("Access-Control-Allow-Origin", "http://localhost:3000/")
  req.headers.set("Access-Control-Allow-Origin", "*")
  req.headers.set("Access-Control-Allow-Methods", "*")

  cors({ origin: "*" })

  const { env, userId, secretKey } = await req.json()

  if (!userId) {
    return NextResponse.json({ error: "userId is missing" }, { status: 400, headers: corsHeaders })
  }

export async function POST(req: NextRequest) {
  // req.headers.set("Access-Control-Allow-Origin", "http://localhost:3000/")
  req.headers.set("Access-Control-Allow-Origin", "*")
  req.headers.set("Access-Control-Allow-Methods", "*")

  cors({ origin: "*" })

  const { env, userId, secretKey } = await req.json()

  if (!userId) {
    return NextResponse.json({ error: "userId is missing" }, { status: 400, headers: corsHeaders })
  }

37 Replies

dys 🐙•3mo ago

What is corsHeaders defined as? Also, you are only showing the error response. What is the successful response? FInally, it is the OPTIONS method that is failing. Does defining POST automatically handle OPTIONS?

NikitaOP•3mo ago

I don't understand what expected answer you want to get Where can I check it? I think you find something you asked for I tried export async function OPTIONS(req: NextRequest, res: NextResponse) {

import { NextRequest, NextResponse } from "next/server"
import cors from "cors"
import { corsHeaders } from "@/consts/corsHeaders"

export async function POST(req: NextRequest, res: NextResponse) {
  console.log(4, "req.method - ", req.method)
  cors({
    origin: ["https://outreach-tool.online", "http://localhost:3000"],
    methods: ["GET", "POST", "OPTIONS"],
    allowedHeaders: ["Content-Type", "x-forwarded-for"],
    credentials: true,
  })

  return NextResponse.json({ res }, { headers: corsHeaders })
}

import { NextRequest, NextResponse } from "next/server"
import cors from "cors"
import { corsHeaders } from "@/consts/corsHeaders"

export async function POST(req: NextRequest, res: NextResponse) {
  console.log(4, "req.method - ", req.method)
  cors({
    origin: ["https://outreach-tool.online", "http://localhost:3000"],
    methods: ["GET", "POST", "OPTIONS"],
    allowedHeaders: ["Content-Type", "x-forwarded-for"],
    credentials: true,
  })

  return NextResponse.json({ res }, { headers: corsHeaders })
}

return NextResponse.json({ res }, { headers: corsHeaders })

dys 🐙•3mo ago

After doing a little reading, I find nothing that suggests that the cors middleware will work like you are using it. There's a nextjs-cors package that seems to adapt the Express cors middleware to work with Next.js, though it's relatively old. Were I you, I'd try creating a middleware.ts and populating it as described here (though you can statically define the CORS options rather than pulling everything in from the environment to make it simpler).

Medium

3 Ways To Configure CORS for NextJS 13 App Router API Route Handlers

Configure Cross-Origin Resource Sharing For NextJS 13 App Router

GitHub

GitHub - yonycalsin/nextjs-cors: :tada: nextjs-cors is a node.js pa...

:tada: nextjs-cors is a node.js package to provide a Connect/Express middleware that can be used to enable CORS with various options :rocket: - yonycalsin/nextjs-cors

NikitaOP•3mo ago

It doesn't work for me as well

import NextCors from "nextjs-cors"
import { NextApiRequest, NextApiResponse } from "next"

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  return res.json({ res })
}

import NextCors from "nextjs-cors"
import { NextApiRequest, NextApiResponse } from "next"

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  return res.json({ res })
}

NikitaOP•3mo ago

My middleware.ts looks like as in medium post

import { NextResponse, type NextRequest } from "next/server"

const corsOptions: {
  allowedMethods: string[]
  allowedOrigins: string[]
  allowedHeaders: string[]
  exposedHeaders: string[]
  maxAge?: number
  credentials: boolean
} = {
  allowedMethods: (process.env?.ALLOWED_METHODS || "").split(","),
  allowedOrigins: (process.env?.ALLOWED_ORIGIN || "").split(","),
  allowedHeaders: (process.env?.ALLOWED_HEADERS || "").split(","),
  exposedHeaders: (process.env?.EXPOSED_HEADERS || "").split(","),
  maxAge: (process.env?.MAX_AGE && parseInt(process.env?.MAX_AGE)) || undefined, // 60 * 60 * 24 * 30, // 30 days
  credentials: process.env?.CREDENTIALS == "true",
}

// Middleware
// ========================================================
// This function can be marked `async` if using `await` inside
export async function middleware(request: NextRequest) {
  // Response
  const response = NextResponse.next()

  // Allowed origins check
  const origin = request.headers.get("origin") ?? ""
  if (corsOptions.allowedOrigins.includes("*") || corsOptions.allowedOrigins.includes(origin)) {
    response.headers.set("Access-Control-Allow-Origin", origin)
  }

  // Set default CORS headers
  response.headers.set("Access-Control-Allow-Credentials", corsOptions.credentials.toString())
  response.headers.set("Access-Control-Allow-Methods", corsOptions.allowedMethods.join(","))
  response.headers.set("Access-Control-Allow-Headers", corsOptions.allowedHeaders.join(","))
  response.headers.set("Access-Control-Expose-Headers", corsOptions.exposedHeaders.join(","))
  response.headers.set("Access-Control-Max-Age", corsOptions.maxAge?.toString() ?? "")

  // Return
  return response
}

// See "Matching Paths" below to learn more
export const config = {
  matcher: "/api/:path*",
}

import { NextResponse, type NextRequest } from "next/server"

const corsOptions: {
  allowedMethods: string[]
  allowedOrigins: string[]
  allowedHeaders: string[]
  exposedHeaders: string[]
  maxAge?: number
  credentials: boolean
} = {
  allowedMethods: (process.env?.ALLOWED_METHODS || "").split(","),
  allowedOrigins: (process.env?.ALLOWED_ORIGIN || "").split(","),
  allowedHeaders: (process.env?.ALLOWED_HEADERS || "").split(","),
  exposedHeaders: (process.env?.EXPOSED_HEADERS || "").split(","),
  maxAge: (process.env?.MAX_AGE && parseInt(process.env?.MAX_AGE)) || undefined, // 60 * 60 * 24 * 30, // 30 days
  credentials: process.env?.CREDENTIALS == "true",
}

// Middleware
// ========================================================
// This function can be marked `async` if using `await` inside
export async function middleware(request: NextRequest) {
  // Response
  const response = NextResponse.next()

  // Allowed origins check
  const origin = request.headers.get("origin") ?? ""
  if (corsOptions.allowedOrigins.includes("*") || corsOptions.allowedOrigins.includes(origin)) {
    response.headers.set("Access-Control-Allow-Origin", origin)
  }

  // Set default CORS headers
  response.headers.set("Access-Control-Allow-Credentials", corsOptions.credentials.toString())
  response.headers.set("Access-Control-Allow-Methods", corsOptions.allowedMethods.join(","))
  response.headers.set("Access-Control-Allow-Headers", corsOptions.allowedHeaders.join(","))
  response.headers.set("Access-Control-Expose-Headers", corsOptions.exposedHeaders.join(","))
  response.headers.set("Access-Control-Max-Age", corsOptions.maxAge?.toString() ?? "")

  // Return
  return response
}

// See "Matching Paths" below to learn more
export const config = {
  matcher: "/api/:path*",
}

I have middleware.ts in project I'm making request to

dys 🐙•3mo ago

Your server is on port 3001.

NikitaOP•3mo ago

yes I'm doing request from 3000 to 3001

dys 🐙•3mo ago

There's no CORS headers though, according to the error. Did you define the appropriate environment variables in a .env file?

NikitaOP•3mo ago

what? I have .env.local file but how its related to CORS? In project 1 (3000) I'm doing request like this

  const response = await fetch(`http://localhost:3001/api/test`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-Forwarded-For": "http://localhost:3000",
    },
    body: JSON.stringify({ env, userId, secretKey }),
    cache: "no-cache",
  })

  const response = await fetch(`http://localhost:3001/api/test`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-Forwarded-For": "http://localhost:3000",
    },
    body: JSON.stringify({ env, userId, secretKey }),
    cache: "no-cache",
  })

dys 🐙•3mo ago

If you look at the corsOptions variable, it is pulling its configuration from the environment.

NikitaOP•3mo ago

I think its wrong

env.local
ALLOWED_METHODS='POST,GET'
ALLOWED_ORIGIN='http://localhost:3000, https://outreach-tool.online'

env.local
ALLOWED_METHODS='POST,GET'
ALLOWED_ORIGIN='http://localhost:3000, https://outreach-tool.online'

I want to allow multiple things

dys 🐙•3mo ago

You have to include OPTIONS.

NikitaOP•3mo ago

Ok Also I think that its worth to mention that I don't have

  allowedHeaders: (process.env?.ALLOWED_HEADERS || "").split(","),
  exposedHeaders: (process.env?.EXPOSED_HEADERS || "").split(","),

  allowedHeaders: (process.env?.ALLOWED_HEADERS || "").split(","),
  exposedHeaders: (process.env?.EXPOSED_HEADERS || "").split(","),

I simply don't know what should I put in there Like that?

ALLOWED_METHODS='OPTIONS'
ALLOWED_ORIGIN='http://localhost:3000, https://outreach-tool.online'

ALLOWED_METHODS='OPTIONS'
ALLOWED_ORIGIN='http://localhost:3000, https://outreach-tool.online'

Even if I copy pasted - still same error

ALLOWED_METHODS="GET, HEAD, PUT, PATCH, POST, DELETE, OPTIONS"
ALLOWED_ORIGIN="https://outreach-tool.online,http://localhost:3000"
ALLOWED_HEADERS="Content-Type, Authorization"
EXPOSED_HEADERS=""
MAX_AGE="86400" # 60 * 60 * 24 = 24 hours
CREDENTIALS="true"
DOMAIN_URL="http://localhost:3001"

ALLOWED_METHODS="GET, HEAD, PUT, PATCH, POST, DELETE, OPTIONS"
ALLOWED_ORIGIN="https://outreach-tool.online,http://localhost:3000"
ALLOWED_HEADERS="Content-Type, Authorization"
EXPOSED_HEADERS=""
MAX_AGE="86400" # 60 * 60 * 24 = 24 hours
CREDENTIALS="true"
DOMAIN_URL="http://localhost:3001"

dys 🐙•3mo ago

Have you restarted the dev server? (Don't know if this will have an effect, but it never hurts.)

NikitaOP•3mo ago

I tried to clear .next and restart pnpm dev on project 1 (3000)

dys 🐙•3mo ago

Well, if anything, you need to restart the server setting the CORS headers, so the one on 3001.

NikitaOP•3mo ago

ok now I deleted .next and restarted project 2 (3001) using pnpm dev And see new error

dys 🐙•3mo ago

What is the HTTP status? (From the Network tab in the developer's tools.)

NikitaOP•3mo ago

IDK

NikitaOP•3mo ago

seems http

dys 🐙•3mo ago

It looks like your request is finally setting the headers, but the request is failing.

NikitaOP•3mo ago

Here is my API route on project 2 (3001) api/test/route.ts

import NextCors from "nextjs-cors"
import { NextApiRequest, NextApiResponse } from "next"
import { NextResponse } from "next/server"

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  return NextResponse.json({}, { status: 200 })
}

import NextCors from "nextjs-cors"
import { NextApiRequest, NextApiResponse } from "next"
import { NextResponse } from "next/server"

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  return NextResponse.json({}, { status: 200 })
}

dys 🐙•3mo ago

You're not defining OPTIONS, so it says HTTP 405: Method Not Allowed.

NikitaOP•3mo ago

How to define OPTIONS? methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE","OPTIONS"], You mean this?

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE", "OPTIONS"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE", "OPTIONS"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

NikitaOP•3mo ago

Still same

dys 🐙•3mo ago

Nope, you're defining a POST handler, but not OPTIONS.

NikitaOP•3mo ago

Like this?

import NextCors from "nextjs-cors"
import { NextApiRequest, NextApiResponse } from "next"
import { NextResponse } from "next/server"

export async function OPTIONS(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE", "OPTIONS"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  return NextResponse.json({}, { status: 200 })
}

import NextCors from "nextjs-cors"
import { NextApiRequest, NextApiResponse } from "next"
import { NextResponse } from "next/server"

export async function OPTIONS(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  await NextCors(req, res, {
    methods: ["GET", "HEAD", "PUT", "PATCH", "POST", "DELETE", "OPTIONS"],
    origin: "https://localhost:3000",
    optionsSuccessStatus: 200,
  })

  return NextResponse.json({}, { status: 200 })
}

NikitaOP•3mo ago

Same

dys 🐙•3mo ago

The middleware should obviate the need for NextCors.

NikitaOP•3mo ago

Also I got error on server

4 req.method -  OPTIONS
 ⨯ TypeError: res.setHeader is not a function

4 req.method -  OPTIONS
 ⨯ TypeError: res.setHeader is not a function

May I call you in discord?

dys 🐙•3mo ago

Sure. There's a #voice-chat channel here we could use.

NikitaOP•3mo ago

Solution project 2 (3001) api/test/route.ts

import { NextApiRequest, NextApiResponse } from "next"
import { NextResponse } from "next/server"

export async function OPTIONS(req: NextApiRequest, res: NextApiResponse) {
  return NextResponse.json({}, { status: 200 })
}

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  return NextResponse.json({}, { status: 200 })
}

import { NextApiRequest, NextApiResponse } from "next"
import { NextResponse } from "next/server"

export async function OPTIONS(req: NextApiRequest, res: NextApiResponse) {
  return NextResponse.json({}, { status: 200 })
}

export async function POST(req: NextApiRequest, res: NextApiResponse) {
  console.log(4, "req.method - ", req.method)

  return NextResponse.json({}, { status: 200 })
}

project 2 (3001) middleware.ts

import { NextResponse, type NextRequest } from "next/server"

const corsOptions: {
  allowedMethods: string[]
  allowedOrigins: string[]
  allowedHeaders: string[]
  exposedHeaders: string[]
  maxAge?: number
  credentials: boolean
} = {
  allowedMethods: (process.env?.ALLOWED_METHODS || "").split(","),
  allowedOrigins: (process.env?.ALLOWED_ORIGIN || "").split(","),
  allowedHeaders: (process.env?.ALLOWED_HEADERS || "").split(","),
  exposedHeaders: (process.env?.EXPOSED_HEADERS || "").split(","),
  maxAge: (process.env?.MAX_AGE && parseInt(process.env?.MAX_AGE)) || undefined, // 60 * 60 * 24 * 30, // 30 days
  credentials: process.env?.CREDENTIALS == "true",
}

// Middleware
// ========================================================
// This function can be marked `async` if using `await` inside
export async function middleware(request: NextRequest) {
  // Response
  const response = NextResponse.next()

  // Allowed origins check
  const origin = request.headers.get("origin") ?? ""
  if (corsOptions.allowedOrigins.includes("*") || corsOptions.allowedOrigins.includes(origin)) {
    response.headers.set("Access-Control-Allow-Origin", origin)
  }

  // Set default CORS headers
  response.headers.set("Access-Control-Allow-Credentials", corsOptions.credentials.toString())
  response.headers.set("Access-Control-Allow-Methods", corsOptions.allowedMethods.join(","))
  response.headers.set("Access-Control-Allow-Headers", corsOptions.allowedHeaders.join(","))
  response.headers.set("Access-Control-Expose-Headers", corsOptions.exposedHeaders.join(","))
  response.headers.set("Access-Control-Max-Age", corsOptions.maxAge?.toString() ?? "")

  // Return
  return response
}

// See "Matching Paths" below to learn more
export const config = {
  matcher: "/api/:path*",
}

import { NextResponse, type NextRequest } from "next/server"

const corsOptions: {
  allowedMethods: string[]
  allowedOrigins: string[]
  allowedHeaders: string[]
  exposedHeaders: string[]
  maxAge?: number
  credentials: boolean
} = {
  allowedMethods: (process.env?.ALLOWED_METHODS || "").split(","),
  allowedOrigins: (process.env?.ALLOWED_ORIGIN || "").split(","),
  allowedHeaders: (process.env?.ALLOWED_HEADERS || "").split(","),
  exposedHeaders: (process.env?.EXPOSED_HEADERS || "").split(","),
  maxAge: (process.env?.MAX_AGE && parseInt(process.env?.MAX_AGE)) || undefined, // 60 * 60 * 24 * 30, // 30 days
  credentials: process.env?.CREDENTIALS == "true",
}

// Middleware
// ========================================================
// This function can be marked `async` if using `await` inside
export async function middleware(request: NextRequest) {
  // Response
  const response = NextResponse.next()

  // Allowed origins check
  const origin = request.headers.get("origin") ?? ""
  if (corsOptions.allowedOrigins.includes("*") || corsOptions.allowedOrigins.includes(origin)) {
    response.headers.set("Access-Control-Allow-Origin", origin)
  }

  // Set default CORS headers
  response.headers.set("Access-Control-Allow-Credentials", corsOptions.credentials.toString())
  response.headers.set("Access-Control-Allow-Methods", corsOptions.allowedMethods.join(","))
  response.headers.set("Access-Control-Allow-Headers", corsOptions.allowedHeaders.join(","))
  response.headers.set("Access-Control-Expose-Headers", corsOptions.exposedHeaders.join(","))
  response.headers.set("Access-Control-Max-Age", corsOptions.maxAge?.toString() ?? "")

  // Return
  return response
}

// See "Matching Paths" below to learn more
export const config = {
  matcher: "/api/:path*",
}

project 2 (3001) .env.local

ALLOWED_METHODS="GET, HEAD, PUT, PATCH, POST, DELETE, OPTIONS"
ALLOWED_ORIGIN="https://outreach-tool.online,http://localhost:3000"
ALLOWED_HEADERS="Content-Type, Authorization, X-Forwarded-For"
EXPOSED_HEADERS=""
MAX_AGE="86400" # 60 * 60 * 24 = 24 hours
CREDENTIALS="true"
DOMAIN_URL="http://localhost:3001"

ALLOWED_METHODS="GET, HEAD, PUT, PATCH, POST, DELETE, OPTIONS"
ALLOWED_ORIGIN="https://outreach-tool.online,http://localhost:3000"
ALLOWED_HEADERS="Content-Type, Authorization, X-Forwarded-For"
EXPOSED_HEADERS=""
MAX_AGE="86400" # 60 * 60 * 24 = 24 hours
CREDENTIALS="true"
DOMAIN_URL="http://localhost:3001"

I'm doing request from project 1 (3000) to project 2 (3001) like this

  const response = await fetch(`http://localhost:3001/api/test`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-Forwarded-For": "http://localhost:3000",
    },
    body: JSON.stringify({ env, userId, secretKey }),
    cache: "no-cache",
  })

  const response = await fetch(`http://localhost:3001/api/test`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "X-Forwarded-For": "http://localhost:3000",
    },
    body: JSON.stringify({ env, userId, secretKey }),
    cache: "no-cache",
  })

NikitaOP•3mo ago

Today I got this error - how to fix that?

NikitaOP•3mo ago

Disable proxy

hgs•3mo ago

In nextjs, rewrite and middleware could solve it

Gaming

Programming

How to fix CORS error in Next.js?