👋 Welcome

Welcome to Fiber's online API documentation, complete with examples to help you start building web applications right away!

Fiber is an Express-inspired web framework built on top of Fasthttp, the fastest HTTP engine for Go. It is designed to facilitate rapid development with zero memory allocations and a strong focus on performance.

These docs cover Fiber v3.

Looking to practice Fiber concepts hands-on? Check out our Learning Resources for interactive challenges and tutorials.

Installation

First, download and install Go. Version 1.25 or higher is required.

Install Fiber using the go get command:

go get github.com/gofiber/fiber/v3

Zero Allocation

Fiber is optimized for high performance, meaning values returned from fiber.Ctx are not immutable by default and will be reused across requests. As a rule of thumb, you should use context values only within the handler and must not keep any references. Once you return from the handler, any values obtained from the context will be reused in future requests. Here is an example:

func handler(c fiber.Ctx) error {
    // Variable is only valid within this handler
    result := c.Params("foo") 

    // ...
}

If you need to persist such values outside the handler, make copies of their underlying buffer using the copy builtin. Here is an example of persisting a string:

func handler(c fiber.Ctx) error {
    // Variable is only valid within this handler
    result := c.Params("foo")

    // Make a copy
    buffer := make([]byte, len(result))
    copy(buffer, result)
    resultCopy := string(buffer) 
    // Variable is now valid indefinitely

    // ...
}

Fiber provides GetString and GetBytes methods on the app that detach values when Immutable is enabled and the data isn't already read-only. If it's disabled, use utils.CopyString and utils.CopyBytes to allocate only when necessary.

app.Get("/:foo", func(c fiber.Ctx) error {
    // Detach if necessary when Immutable is enabled
    result := c.App().GetString(c.Params("foo"))

    // ...
})

Alternatively, you can enable the Immutable setting. This makes all values returned from the context immutable, allowing you to persist them anywhere. Note that this comes at the cost of performance.

app := fiber.New(fiber.Config{
    Immutable: true,
})

For more information, please refer to #426, #185, and #3012.

Hello, World

Here is the simplest Fiber application you can create:

package main

import "github.com/gofiber/fiber/v3"

func main() {
    app := fiber.New()

    app.Get("/", func(c fiber.Ctx) error {
        return c.SendString("Hello, World!")
    })

    app.Listen(":3000")
}

go run server.go

Browse to http://localhost:3000 and you should see Hello, World! displayed on the page.

Basic Routing

Routing determines how an application responds to a client request at a particular endpoint—a combination of path and HTTP request method (GET, PUT, POST, etc.).

Each route can have multiple handler functions that are executed when the route is matched.

Route definitions follow the structure below:

// Function signature
app.Method(path string, ...func(fiber.Ctx) error)

• app is an instance of Fiber
• Method is an HTTP request method: GET, PUT, POST, etc.
• path is a virtual path on the server
• func(fiber.Ctx) error is a callback function containing the Context executed when the route is matched

Simple Route

// Respond with "Hello, World!" on root path "/"
app.Get("/", func(c fiber.Ctx) error {
    return c.SendString("Hello, World!")
})

Parameters

// GET http://localhost:8080/hello%20world

app.Get("/:value", func(c fiber.Ctx) error {
    return c.SendString("value: " + c.Params("value"))
    // => Response: "value: hello world"
})

Optional Parameter

// GET http://localhost:3000/john

app.Get("/:name?", func(c fiber.Ctx) error {
    if c.Params("name") != "" {
        return c.SendString("Hello " + c.Params("name"))
        // => Response: "Hello john"
    }
    return c.SendString("Where is john?")
    // => Response: "Where is john?"
})

Wildcards

// GET http://localhost:3000/api/user/john

app.Get("/api/*", func(c fiber.Ctx) error {
    return c.SendString("API path: " + c.Params("*"))
    // => Response: "API path: user/john"
})

Static Files

To serve static files such as images, CSS, and JavaScript files, use the static middleware.

Use the following code to serve files in a directory named ./public:

package main

import (
    "github.com/gofiber/fiber/v3"
    "github.com/gofiber/fiber/v3/middleware/static"
)

func main() {
    app := fiber.New()

    app.Use("/", static.New("./public"))

    app.Listen(":3000")
}

Now, you can access the files in the ./public directory via your browser:

http://localhost:3000/hello.html
http://localhost:3000/js/jquery.js
http://localhost:3000/css/style.css