gin-contrib/cors

• gin-contrib/cors
  • Overview
  • Installation
  • Quick Start
  • Advanced Usage
    • Custom Configuration
    • DefaultConfig Reference
    • Default() Convenience
  • Configuration Reference
    • Notes on Configuration
    • Examples
      • Advanced Options
      • Custom Origin Validation
      • With Gin Context
  • Helper Methods
  • Validation & Error Handling
  • Important Notes

---

Overview

CORS (Cross-Origin Resource Sharing) middleware for Gin.

• Enables flexible CORS handling for your Gin-based APIs.
• Highly configurable: origins, methods, headers, credentials, and more.

---

Installation

go get github.com/gin-contrib/cors

Import in your Go code:

import "github.com/gin-contrib/cors"

---

Quick Start

Allow all origins (default):

import (
  "github.com/gin-contrib/cors"
  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  router.Use(cors.Default()) // All origins allowed by default
  router.Run()
}

⚠️ Warning: Allowing all origins disables cookies for clients. For credentialed requests, do not allow all origins.

---

Advanced Usage

Custom Configuration

Configure allowed origins, methods, headers, and more:

import (
  "time"
  "github.com/gin-contrib/cors"
  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  router.Use(cors.New(cors.Config{
    AllowOrigins:     []string{"https://foo.com"},
    AllowMethods:     []string{"PUT", "PATCH"},
    AllowHeaders:     []string{"Origin"},
    ExposeHeaders:    []string{"Content-Length"},
    AllowCredentials: true,
    AllowOriginFunc: func(origin string) bool {
      return origin == "https://github.com"
    },
    MaxAge: 12 * time.Hour,
  }))
  router.Run()
}

---

DefaultConfig Reference

Start with library defaults and customize as needed:

import (
  "github.com/gin-contrib/cors"
  "github.com/gin-gonic/gin"
)

func main() {
  router := gin.Default()
  config := cors.DefaultConfig()
  config.AllowOrigins = []string{"http://google.com"}
  // config.AllowOrigins = []string{"http://google.com", "http://facebook.com"}
  // config.AllowAllOrigins = true

  router.Use(cors.New(config))
  router.Run()
}

Note: Default() allows all origins, but DefaultConfig() does not. To allow all origins, set AllowAllOrigins = true.

---

Default() Convenience

Enable all origins with a single call:

router.Use(cors.Default()) // Equivalent to AllowAllOrigins = true

---

Configuration Reference

The middleware is controlled via the cors.Config struct. All fields are optional unless otherwise stated.

Field	Type	Default	Description
AllowAllOrigins	bool	false	If true, allows all origins. Credentials cannot be used.
AllowOrigins	[]string	[]	List of allowed origins. Supports exact match, *, and wildcards.
AllowOriginFunc	func(string) bool	nil	Custom function to validate origin. If set, AllowOrigins is ignored.
AllowOriginWithContextFunc	func(*gin.Context,string)bool	nil	Like AllowOriginFunc, but with request context.
AllowMethods	[]string	[]string{"GET", "POST", "PUT", "PATCH", "DELETE", "HEAD", "OPTIONS"}	Allowed HTTP methods.
AllowPrivateNetwork	bool	false	Adds Private Network Access CORS header.
AllowHeaders	[]string	[]	List of non-simple headers permitted in requests.
AllowCredentials	bool	false	Allow cookies, HTTP auth, or client certs. Only if precise origins are used.
ExposeHeaders	[]string	[]	Headers exposed to the browser.
MaxAge	time.Duration	12 * time.Hour	Cache time for preflight requests.
AllowWildcard	bool	false	Enables wildcards in origins (e.g. https://*.example.com).
AllowBrowserExtensions	bool	false	Allow browser extension schemes as origins (e.g. chrome-extension://).
CustomSchemas	[]string	nil	Additional allowed URI schemes (e.g. tauri://).
AllowWebSockets	bool	false	Allow ws:// and wss:// schemas.
AllowFiles	bool	false	Allow file:// origins (dangerous; use only if necessary).
OptionsResponseStatusCode	int	204	Custom status code for OPTIONS responses.

---

Notes on Configuration

• Only one of AllowAllOrigins, AllowOrigins, AllowOriginFunc, or AllowOriginWithContextFunc should be set.
• If AllowAllOrigins is true, other origin settings are ignored and credentialed requests are not allowed.
• If AllowWildcard is enabled, only one * is allowed per origin string.
• Use AllowBrowserExtensions, AllowWebSockets, or AllowFiles to permit non-HTTP(s) protocols as origins.
• Custom schemas allow, for example, usage in desktop apps via custom URI schemes (tauri://, etc.).
• If both AllowOriginFunc and AllowOriginWithContextFunc are set, the context-specific function is preferred.

---

Examples

Advanced Options

config := cors.Config{
  AllowOrigins:           []string{"https://*.foo.com", "https://bar.com"},
  AllowWildcard:          true,
  AllowMethods:           []string{"GET", "POST"},
  AllowHeaders:           []string{"Authorization", "Content-Type"},
  AllowCredentials:       true,
  AllowBrowserExtensions: true,
  AllowWebSockets:        true,
  AllowFiles:             false,
  CustomSchemas:          []string{"tauri://"},
  MaxAge:                 24 * time.Hour,
  ExposeHeaders:          []string{"X-Custom-Header"},
  AllowPrivateNetwork:    true,
}

Custom Origin Validation

config := cors.Config{
  AllowOriginFunc: func(origin string) bool {
    // Allow any github.com subdomain or a custom rule
    return strings.HasSuffix(origin, "github.com")
  },
}

With Gin Context

config := cors.Config{
  AllowOriginWithContextFunc: func(c *gin.Context, origin string) bool {
    // Allow only if a certain header is present
    return c.Request.Header.Get("X-Allow-CORS") == "yes"
  },
}

---

Helper Methods

Dynamically add methods or headers to the config:

config.AddAllowMethods("DELETE", "OPTIONS")
config.AddAllowHeaders("X-My-Header")
config.AddExposeHeaders("X-Other-Header")

---

Validation & Error Handling

• Calling Validate() on a Config checks for misconfiguration (called internally).
• If AllowAllOrigins is set, you cannot also set AllowOrigins or any AllowOriginFunc.
• If neither AllowAllOrigins, AllowOriginFunc, nor AllowOrigins is set, an error is raised.
• If an AllowOrigin contains a wildcard but AllowWildcard is not enabled, or more than one * is present, a panic is triggered.
• Invalid origin schemas or unsupported wildcards are rejected.

---

Important Notes

• Enabling all origins disables cookies: When AllowAllOrigins is enabled, Gin cannot set cookies for clients. If you need credential sharing (cookies, authentication headers), do not allow all origins.
• For detailed documentation and configuration options, see the GoDoc.