🔌 Routing - Fiber

import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem'; import RoutingHandler from './../partials/routing/handler.md';

Handlers

Automatic HEAD routes

Fiber automatically registers a HEAD route for every GET route you add. The generated handler chain mirrors the GET chain, so HEAD requests reuse middleware, status codes, and headers while the response body is suppressed.

app := fiber.New()

app.Get("/users/:id", func(c fiber.Ctx) error {
    c.Set("X-User", c.Params("id"))
    return c.SendStatus(fiber.StatusOK)
})

// HEAD /users/:id now returns the same headers and status without a body.

You can still register dedicated HEAD handlers—even with auto-registration enabled—and Fiber replaces the generated route so your implementation wins:

app.Head("/users/:id", func(c fiber.Ctx) error {
    return c.SendStatus(fiber.StatusNoContent)
})

To opt out globally, start the app with DisableHeadAutoRegister:

handler := func(c fiber.Ctx) error {
    c.Set("X-User", c.Params("id"))
    return c.SendStatus(fiber.StatusOK)
}

app := fiber.New(fiber.Config{DisableHeadAutoRegister: true})
app.Get("/users/:id", handler) // HEAD /users/:id now returns 405 unless you add it manually.

Auto-generated HEAD routes participate in every router scope, including Group hierarchies, mounted sub-apps, parameterized and wildcard paths, and static file helpers. They also appear in route listings such as app.Stack() so tooling sees both the GET and HEAD entries.

Paths

A route path paired with an HTTP method defines an endpoint. It can be a plain string or a pattern.

Examples of route paths based on strings

// This route path will match requests to the root route, "/":
app.Get("/", func(c fiber.Ctx) error {
    return c.SendString("root")
})

// This route path will match requests to "/about":
app.Get("/about", func(c fiber.Ctx) error {
    return c.SendString("about")
})

// This route path will match requests to "/random.txt":
app.Get("/random.txt", func(c fiber.Ctx) error {
    return c.SendString("random.txt")
})

As with the Express.js framework, the order in which routes are declared matters. Routes are evaluated sequentially, so more specific paths should appear before those with variables.

:::info Place routes with variable parameters after fixed paths to avoid unintended matches. :::

Parameters

Route parameters are dynamic segments in a path, either named or unnamed, used to capture values from the URL. Retrieve them with the Params function using the parameter name or, for unnamed parameters, the wildcard (*) or plus (+) symbol with an index.

The characters :, +, and * introduce parameters.

Use * or + to capture segments greedily.

You can define optional parameters by appending ? to a named segment. The + sign is greedy and required, while * acts as an optional greedy wildcard.

Example of defining routes with route parameters

// Parameters
app.Get("/user/:name/books/:title", func(c fiber.Ctx) error {
    fmt.Fprintf(c, "%s\n", c.Params("name"))
    fmt.Fprintf(c, "%s\n", c.Params("title"))
    return nil
})
// Plus - greedy - not optional
app.Get("/user/+", func(c fiber.Ctx) error {
    return c.SendString(c.Params("+"))
})

// Optional parameter
app.Get("/user/:name?", func(c fiber.Ctx) error {
    return c.SendString(c.Params("name"))
})

// Wildcard - greedy - optional
app.Get("/user/*", func(c fiber.Ctx) error {
    return c.SendString(c.Params("*"))
})

// This route path will match requests to "/v1/some/resource/name:customVerb", since the parameter character is escaped
app.Get(`/v1/some/resource/name\:customVerb`, func(c fiber.Ctx) error {
    return c.SendString("Hello, Community")
})

:::info The hyphen (-) and dot (.) are treated literally, so you can combine them with route parameters. :::

:::info Escape special parameter characters with \\ to treat them literally. This technique is useful for custom methods like those in the Google API Design Guide. Wrap routes in backticks to keep escape sequences clear. :::

// http://localhost:3000/plantae/prunus.persica
app.Get("/plantae/:genus.:species", func(c fiber.Ctx) error {
    fmt.Fprintf(c, "%s.%s\n", c.Params("genus"), c.Params("species"))
    return nil // prunus.persica
})

// http://localhost:3000/flights/LAX-SFO
app.Get("/flights/:from-:to", func(c fiber.Ctx) error {
    fmt.Fprintf(c, "%s-%s\n", c.Params("from"), c.Params("to"))
    return nil // LAX-SFO
})

Fiber's router detects when these characters belong to the literal path and handles them accordingly.

// http://localhost:3000/shop/product/color:blue/size:xs
app.Get("/shop/product/color::color/size::size", func(c fiber.Ctx) error {
    fmt.Fprintf(c, "%s:%s\n", c.Params("color"), c.Params("size"))
    return nil // blue:xs
})

You can chain multiple named or unnamed parameters—including wildcard and plus segments—giving the router greater flexibility.

// GET /@v1
// Params: "sign" -> "@", "param" -> "v1"
app.Get("/:sign:param", handler)

// GET /api-v1
// Params: "name" -> "v1"
app.Get("/api-:name", handler)

// GET /customer/v1/cart/proxy
// Params: "*1" -> "customer/", "*2" -> "/cart"
app.Get("/*v1*/proxy", handler)

// GET /v1/brand/4/shop/blue/xs
// Params: "*1" -> "brand/4", "*2" -> "blue/xs"
app.Get("/v1/*/shop/*", handler)

Fiber's routing is inspired by Express but intentionally omits regular expression routes due to their performance cost. You can try similar patterns using the Express route tester (v0.1.7).

Constraints

Route constraints execute when a match has occurred to the incoming URL and the URL path is tokenized into route values by parameters. The feature was introduced in v2.37.0 and inspired by .NET Core.

:::caution Constraints aren't validation for parameters. If constraints aren't valid for a parameter value, Fiber returns 404 handler. :::

Constraint	Example	Example matches
int	`:id<int>`	123456789, -123456789
bool	`:active<bool>`	true,false
guid	`:id<guid>`	CD2C1638-1638-72D5-1638-DEADBEEF1638
float	`:weight<float>`	1.234, -1,001.01e8
minLen(value)	`:username<minLen(4)>`	Test (must be at least 4 characters)
maxLen(value)	`:filename<maxLen(8)>`	MyFile (must be no more than 8 characters
len(length)	`:filename<len(12)>`	somefile.txt (exactly 12 characters)
min(value)	`:age<min(18)>`	19 (Integer value must be at least 18)
max(value)	`:age<max(120)>`	91 (Integer value must be no more than 120)
range(min,max)	`:age<range(18,120)>`	91 (Integer value must be at least 18 but no more than 120)
alpha	`:name<alpha>`	Rick (String must consist of one or more alphabetical characters, a-z and case-insensitive)
datetime	`:dob<datetime(2006\\-01\\-02)>`	2005-11-01
regex(expression)	`:date<regex(\d{4}-\d{2}-\d{2})>`	2022-08-27 (Must match regular expression)

Examples

app.Get("/:test<min(5)>", func(c fiber.Ctx) error {
    return c.SendString(c.Params("test"))
})

// curl -X GET http://localhost:3000/12
// 12

// curl -X GET http://localhost:3000/1
// Not Found

</TabItem> <TabItem value="multiple-constraints" label="Multiple Constraints">

You can use ; for multiple constraints.

app.Get("/:test<min(100);maxLen(5)>", func(c fiber.Ctx) error {
    return c.SendString(c.Params("test"))
})

// curl -X GET http://localhost:3000/120000
// Not Found

// curl -X GET http://localhost:3000/1
// Not Found

// curl -X GET http://localhost:3000/250
// 250

</TabItem> <TabItem value="regex-constraint" label="Regex Constraint">

Fiber precompiles the regex when registering routes, so regex constraints add no runtime overhead.

app.Get(`/:date<regex(\d{4}-\d{2}-\d{2})>`, func(c fiber.Ctx) error {
    return c.SendString(c.Params("date"))
})

// curl -X GET http://localhost:3000/125
// Not Found

// curl -X GET http://localhost:3000/test
// Not Found

// curl -X GET http://localhost:3000/2022-08-27
// 2022-08-27

</TabItem> </Tabs>

:::caution Prefix routing characters with \\ when using the datetime constraint (*, +, ?, :, /, <, >, ;, (, )), to avoid misparsing. :::

Optional Parameter Example

You can impose constraints on optional parameters as well.

app.Get("/:test<int>?", func(c fiber.Ctx) error {
  return c.SendString(c.Params("test"))
})
// curl -X GET http://localhost:3000/42
// 42
// curl -X GET http://localhost:3000/
//
// curl -X GET http://localhost:3000/7.0
// Not Found

Custom Constraint

Custom constraints can be added to Fiber using the app.RegisterCustomConstraint method. Your constraints have to be compatible with the CustomConstraint interface.

:::caution Attention, custom constraints can now override built-in constraints. If a custom constraint has the same name as a built-in constraint, the custom constraint will be used instead. This allows for more flexibility in defining route parameter constraints. :::

Add external constraints when you need stricter rules, such as verifying that a parameter is a valid ULID.

// CustomConstraint is an interface for custom constraints
type CustomConstraint interface {
    // Name returns the name of the constraint.
    // This name is used in the constraint matching.
    Name() string

    // Execute executes the constraint.
    // It returns true if the constraint is matched and right.
    // param is the parameter value to check.
    // args are the constraint arguments.
    Execute(param string, args ...string) bool
}

You can check the example below:

type UlidConstraint struct {
    fiber.CustomConstraint
}

func (*UlidConstraint) Name() string {
    return "ulid"
}

func (*UlidConstraint) Execute(param string, args ...string) bool {
    _, err := ulid.Parse(param)
    return err == nil
}

func main() {
    app := fiber.New()
    app.RegisterCustomConstraint(&UlidConstraint{})

    app.Get("/login/:id<ulid>", func(c fiber.Ctx) error {
        return c.SendString("...")
    })

    app.Listen(":3000")

    // /login/01HK7H9ZE5BFMK348CPYP14S0Z -> 200
    // /login/12345 -> 404
}

Middleware

Functions that are designed to make changes to the request or response are called middleware functions. The Next is a Fiber router function, when called, executes the next function that matches the current route.

Example of a middleware function

app.Use(func(c fiber.Ctx) error {
    // Set a custom header on all responses:
    c.Set("X-Custom-Header", "Hello, World")

    // Go to next middleware:
    return c.Next()
})

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

Use method path is a mount, or prefix path, and limits middleware to only apply to any paths requested that begin with it.

:::note Prefix matches must now end at a slash boundary (or be an exact match). For example, /api runs for /api and /api/users but no longer for /apiv2. Parameter tokens such as :name, :name?, *, and + are still expanded before this boundary check runs. :::

Constraints on Adding Routes Dynamically

:::caution Adding routes dynamically after the application has started is not supported due to design and performance considerations. Make sure to define all your routes before the application starts. :::

Grouping

If you have many endpoints, you can organize your routes using Group.

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

    api := app.Group("/api", middleware) // /api

    v1 := api.Group("/v1", middleware)   // /api/v1
    v1.Get("/list", handler)             // /api/v1/list
    v1.Get("/user", handler)             // /api/v1/user

    v2 := api.Group("/v2", middleware)   // /api/v2
    v2.Get("/list", handler)             // /api/v2/list
    v2.Get("/user", handler)             // /api/v2/user

    log.Fatal(app.Listen(":3000"))
}

More information about this in our Grouping Guide