CORS

Using cors field you can emulate CORS behavior (headers, credentials) to mirror how a real backend would respond. For more details about CORS, see.

Quick Example

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      origin: ['http://localhost:3000', /\.example\.com$/],
      methods: ['GET'],
      allowedHeaders: ['accept'],
      exposedHeaders: ['accept'],
      maxAge: 3600,
      credentials: true
    }
  },
  ...
];

Type: ((request: Request) => CorsOrigin | Promise<CorsOrigin>) | CorsOrigin
Defines which origins are allowed to access the server. Use a string for a single origin, a RegExp for pattern matching, an array for multiple origins, or a function for dynamic rules.

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      origin: ['https://example.com', /\.example\.com$/]
    }
  },
  ...
];

methods

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      methods: ['GET', 'POST', 'OPTIONS']
    }
  },
  ...
];

allowedHeaders

Type: string[]
Allowed request headers. Default is *. List the headers your client actually sends.

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      allowedHeaders: ['Content-Type', 'Authorization']
    }
  },
  ...
];

exposedHeaders

Type: string[]
Response headers exposed to browser JavaScript. Default is *. Use this when the frontend needs to read custom response headers.

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      exposedHeaders: ['X-Request-Id']
    }
  },
  ...
];

credentials

Type: boolean
Whether to expose the response to frontend JavaScript when using credentials. Default is true. Enable when you use credentials: "include" on the client (cookies, auth).

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      origin: 'https://app.example.com',
      credentials: true
    }
  },
  ...
];

maxAge

Type: number
How long the preflight response can be cached (in seconds). Default is 3600. Increasing maxAge reduces preflight requests.

import type { MockServerConfig } from 'mock-config-server';

export const mockServerConfig: MockServerConfig = [
  {
    cors: {
      maxAge: 600
    }
  },
  ...
];