fiber/docs/api/middleware/cors.md

id, title

id	title
cors	CORS

CORS middleware for Fiber that can be used to enable Cross-Origin Resource Sharing with various options.

Signatures

func New(config ...Config) fiber.Handler

Examples

Import the middleware package that is part of the Fiber web framework

import (
  "github.com/gofiber/fiber/v2"
  "github.com/gofiber/fiber/v2/middleware/cors"
)

After you initiate your Fiber app, you can use the following possibilities:

// Initialize default config
app.Use(cors.New())

// Or extend your config for customization
app.Use(cors.New(cors.Config{
    AllowOrigins: "https://gofiber.io, https://gofiber.net",
    AllowHeaders:  "Origin, Content-Type, Accept",
}))

Using the AllowOriginsFunc function. In this example any origin will be allowed via CORS.

For example, if a browser running on http://localhost:3000 sends a request, this will be accepted and the access-control-allow-origin response header will be set to http://localhost:3000.

Note: Using this feature is discouraged in production and it's best practice to explicitly set CORS origins via AllowOrigins.

app.Use(cors.New())

app.Use(cors.New(cors.Config{
    AllowOriginsFunc: func(origin string) bool {
        return os.Getenv("ENVIRONMENT") == "development"
    },
}))

Config

// Config defines the config for middleware.
type Config struct {
	// Next defines a function to skip this middleware when returned true.
	//
	// Optional. Default: nil
	Next func(c *fiber.Ctx) bool

	// AllowOriginsFunc defines a function that will set the 'access-control-allow-origin'
	// response header to the 'origin' request header when returned true.
	// 
	// Note: Using this feature is discouraged in production and it's best practice to explicitly
	// set CORS origins via 'AllowOrigins'
	//
	// Optional. Default: nil
	AllowOriginsFunc func(origin string) bool

	// AllowOrigin defines a list of origins that may access the resource.
	//
	// Optional. Default value "*"
	AllowOrigins string

	// AllowMethods defines a list methods allowed when accessing the resource.
	// This is used in response to a preflight request.
	//
	// Optional. Default value "GET,POST,HEAD,PUT,DELETE,PATCH"
	AllowMethods string

	// AllowHeaders defines a list of request headers that can be used when
	// making the actual request. This is in response to a preflight request.
	//
	// Optional. Default value "".
	AllowHeaders string

	// AllowCredentials indicates whether or not the response to the request
	// can be exposed when the credentials flag is true. When used as part of
	// a response to a preflight request, this indicates whether or not the
	// actual request can be made using credentials.
	//
	// Optional. Default value false.
	AllowCredentials bool

	// ExposeHeaders defines a whitelist headers that clients are allowed to
	// access.
	//
	// Optional. Default value "".
	ExposeHeaders string

	// MaxAge indicates how long (in seconds) the results of a preflight request
	// can be cached.
	//
	// Optional. Default value 0.
	MaxAge int
}

Default Config

var ConfigDefault = Config{
	Next:         nil,
	AllowOriginsFunc: nil,
	AllowOrigins: "*",
	AllowMethods: strings.Join([]string{
		fiber.MethodGet,
		fiber.MethodPost,
		fiber.MethodHead,
		fiber.MethodPut,
		fiber.MethodDelete,
		fiber.MethodPatch,
	}, ","),
	AllowHeaders:     "",
	AllowCredentials: false,
	ExposeHeaders:    "",
	MaxAge:           0,
}