EarlyData

The Early Data middleware adds TLS 1.3 "0-RTT" support to Fiber. When the client and server share a PSK, TLS 1.3 lets the client send data with the first flight and skip the initial round trip.

Enable Fiber's TrustProxy option before using this middleware to avoid spoofed client headers.

Enabling early data in a reverse proxy (for example, ssl_early_data on; in nginx) makes requests replayable. Review these resources before proceeding:

• datatracker
• trailofbits

By default, the middleware permits early data only for safe methods (GET, HEAD, OPTIONS, TRACE) and rejects other requests before your handler runs. Override this behavior with the AllowEarlyData option.

Signatures

func New(config ...Config) fiber.Handler
func IsEarly(c fiber.Ctx) bool

IsEarly returns true when a request used early data and the middleware allowed it to proceed.

Examples

Import the middleware package:

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

Once your Fiber app is initialized, use the middleware like this:

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

// Or extend your config for customization
app.Use(earlydata.New(earlydata.Config{
    Error: fiber.ErrTooEarly,
    // ...
}))

Config

Property	Type	Description	Default
Next	func(fiber.Ctx) bool	Skip this middleware when the function returns true.	nil
IsEarlyData	func(fiber.Ctx) bool	Reports whether the request used early data.	Function checking if "Early-Data" header equals "1"
AllowEarlyData	func(fiber.Ctx) bool	Decides if an early-data request should be allowed.	Function rejecting on unsafe and allowing safe methods
Error	error	Returned when an early-data request is rejected.	fiber.ErrTooEarly

Default Config

var ConfigDefault = Config{
    IsEarlyData: func(c fiber.Ctx) bool {
        return c.Get(DefaultHeaderName) == DefaultHeaderTrueValue
    },
    AllowEarlyData: func(c fiber.Ctx) bool {
        return fiber.IsMethodSafe(c.Method())
    },
    Error: fiber.ErrTooEarly,
}

Constants

const (
    DefaultHeaderName      = "Early-Data"
    DefaultHeaderTrueValue = "1"
)