📦 Fiber

Server start

New

This method creates a new App named instance. You can pass optional config when creating a new instance.

Signature

func New(config ...Config) *App

Example

// Default config
app := fiber.New()

// ...

Config

You can pass an optional Config when creating a new Fiber instance.

Example

// Custom config
app := fiber.New(fiber.Config{
    CaseSensitive: true,
    StrictRouting: true,
    ServerHeader:  "Fiber",
    AppName: "Test App v1.0.1",
})

// ...

Config fields

Property	Type	Description	Default
AppName	string	Sets the application name used in logs and the Server header	""
BodyLimit	int	Sets the maximum allowed size for a request body. Zero or negative values fall back to the default limit. If the size exceeds the configured limit, it sends 413 - Request Entity Too Large response. This limit also applies when running Fiber through the adaptor middleware from net/http.	4 * 1024 * 1024
CaseSensitive	bool	When enabled, /Foo and /foo are different routes. When disabled, /Foo and /foo are treated the same.	false
CBORDecoder	utils.CBORUnmarshal	Allowing for flexibility in using another cbor library for decoding.	binder.UnimplementedCborUnmarshal
CBOREncoder	utils.CBORMarshal	Allowing for flexibility in using another cbor library for encoding.	binder.UnimplementedCborMarshal
ColorScheme	Colors	You can define custom color scheme. They'll be used for startup message, route list and some middlewares.	DefaultColors
CompressedFileSuffixes	map[string]string	Adds a suffix to the original file name and tries saving the resulting compressed file under the new file name.	{"gzip": ".fiber.gz", "br": ".fiber.br", "zstd": ".fiber.zst"}
Concurrency	int	Maximum number of concurrent connections.	256 * 1024
DisableDefaultContentType	bool	When true, omits the default Content-Type header from the response.	false
DisableDefaultDate	bool	When true, omits the Date header from the response.	false
DisableHeadAutoRegister	bool	Prevents Fiber from automatically registering HEAD routes for each GET route so you can supply custom HEAD handlers; manual HEAD routes still override the generated ones.	false
DisableHeaderNormalizing	bool	By default all header names are normalized: conteNT-tYPE -> Content-Type	false
DisableKeepalive	bool	Disables keep-alive connections so the server closes each connection after the first response.	false
DisablePreParseMultipartForm	bool	Will not pre parse Multipart Form data if set to true. This option is useful for servers that desire to treat multipart form data as a binary blob, or choose when to parse the data.	false
EnableIPValidation	bool	If set to true, c.IP() and c.IPs() will validate IP addresses before returning them. Also, c.IP() will return only the first valid IP rather than just the raw header value that may be a comma separated string. WARNING: There is a small performance cost to doing this validation. Keep disabled if speed is your only concern and your application is behind a trusted proxy that already validates this header.	false
EnableSplittingOnParsers	bool	Splits query, body, and header parameters on commas when enabled. For example, /api?foo=bar,baz becomes foo[]=bar&foo[]=baz.	false
ErrorHandler	ErrorHandler	ErrorHandler is executed when an error is returned from fiber.Handler. Mounted fiber error handlers are retained by the top-level app and applied on prefix associated requests.	DefaultErrorHandler
GETOnly	bool	Rejects all non-GET requests if set to true. This option is useful as anti-DoS protection for servers accepting only GET requests. The request size is limited by ReadBufferSize if GETOnly is set.	false
IdleTimeout	time.Duration	The maximum amount of time to wait for the next request when keep-alive is enabled. If IdleTimeout is zero, the value of ReadTimeout is used.	0
Immutable	bool	When enabled, all values returned by context methods are immutable. By default, they are valid until you return from the handler; see issue #185.	false
JSONDecoder	utils.JSONUnmarshal	Allowing for flexibility in using another json library for decoding.	json.Unmarshal
JSONEncoder	utils.JSONMarshal	Allowing for flexibility in using another json library for encoding.	json.Marshal
MaxRanges	int	Sets the maximum number of ranges parsed from a Range header. Zero or negative values fall back to the default limit. If the limit is exceeded, the request is rejected with 416 - Requested Range Not Satisfiable and Content-Range: bytes */<size>.	16
MsgPackDecoder	utils.MsgPackUnmarshal	Allowing for flexibility in using another msgpack library for decoding.	binder.UnimplementedMsgpackUnmarshal
MsgPackEncoder	utils.MsgPackMarshal	Allowing for flexibility in using another msgpack library for encoding.	binder.UnimplementedMsgpackMarshal
PassLocalsToContext	bool	Controls whether StoreInContext also propagates values into the request context.Context for Fiber-backed contexts. StoreInContext always writes to c.Locals(). ValueFromContext for Fiber-backed contexts always reads from c.Locals().	false
PassLocalsToViews	bool	PassLocalsToViews Enables passing of the locals set on a fiber.Ctx to the template engine. See our Template Middleware for supported engines.	false
ProxyHeader	string	Specifies the header name to read the client's real IP address from when behind a reverse proxy. Common values: fiber.HeaderXForwardedFor, "X-Real-IP", "CF-Connecting-IP" (Cloudflare). Important: This setting requires TrustProxy to be enabled; TrustProxyConfig controls which proxy IPs are trusted for reading this header. Without TrustProxy, this setting has no effect and c.IP() will always return the remote IP from the TCP connection. Behavior note: X-Forwarded-For often contains a comma-separated chain of IP addresses. With the default EnableIPValidation = false, c.IP() will return the raw header value (the whole chain) rather than a single parsed client IP. With EnableIPValidation = true, c.IP() parses the header and returns the first syntactically valid IP address it finds; it does not walk the chain to find the first non-proxy hop. For a reliable client IP, configure your reverse proxy to overwrite or sanitize this header and/or to provide a single-IP header such as "X-Real-IP" or a provider-specific header like "CF-Connecting-IP". Security Warning: Headers can be easily spoofed. Always configure TrustProxyConfig to validate the proxy IP address, otherwise malicious clients can forge headers to bypass IP-based access controls.	""
ReadBufferSize	int	per-connection buffer size for requests' reading. This also limits the maximum header size. Increase this buffer if your clients send multi-KB RequestURIs and/or multi-KB headers (for example, BIG cookies).	4096
ReadTimeout	time.Duration	The amount of time allowed to read the full request, including the body. The default timeout is unlimited.	0
ReduceMemoryUsage	bool	Aggressively reduces memory usage at the cost of higher CPU usage if set to true.	false
RequestMethods	[]string	RequestMethods provides customizability for HTTP methods. You can add/remove methods as you wish.	DefaultMethods
ServerHeader	string	Enables the Server HTTP header with the given value.	""
StreamRequestBody	bool	StreamRequestBody enables request body streaming, and calls the handler sooner when given body is larger than the current limit.	false
StrictRouting	bool	When enabled, the router treats /foo and /foo/ as different. Otherwise, the router treats /foo and /foo/ as the same.	false
StructValidator	StructValidator	If you want to validate header/form/query... automatically when to bind, you can define struct validator. Fiber doesn't have default validator, so it'll skip validator step if you don't use any validator.	nil
TrustProxy	bool	Enables trust of reverse proxy headers. When enabled, Fiber will check if the request is coming from a trusted proxy (configured in TrustProxyConfig) before reading values from proxy headers. Required for: Using ProxyHeader to read client IP from headers like X-Forwarded-For. Behavior when enabled: If the remote IP is trusted (matches TrustProxyConfig), then c.IP() reads from ProxyHeader (when configured; otherwise it uses RemoteIP()), c.Scheme() first checks standard proxy scheme headers (X-Forwarded-Proto, X-Forwarded-Protocol, X-Forwarded-Ssl, X-Url-Scheme) and falls back to the actual connection scheme if none are set, and c.Hostname() prefers X-Forwarded-Host but falls back to the request Host header when the proxy header is not present. If the remote IP is NOT trusted, these methods ignore proxy headers and use the actual connection values instead. Security: This prevents header spoofing by validating the proxy's IP address. Always configure TrustProxyConfig when enabling this option and set ProxyHeader if you want c.IP() to use a specific header.	false
TrustProxyConfig	TrustProxyConfig	Configures which proxy IP addresses or ranges to trust. Only effective when TrustProxy is enabled. Fields: • Proxies - List of trusted proxy IPs or CIDR ranges (e.g., []string{"10.10.0.58", "192.168.0.0/24"}) • Loopback - Trust loopback addresses (127.0.0.0/8, ::1/128) • Private - Trust all private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, fc00::/7) • LinkLocal - Trust link-local addresses (169.254.0.0/16, fe80::/10) • UnixSocket - Trust Unix domain socket connections Example: For an app behind Nginx at 10.10.0.58, use TrustProxyConfig{Proxies: []string{"10.10.0.58"}} or TrustProxyConfig{Private: true} if using private network IPs.	{}
UnescapePath	bool	Converts all encoded characters in the route back before setting the path for the context, so that the routing can also work with URL encoded special characters	false
Views	Views	Views is the interface that wraps the Render function. See our Template Middleware for supported engines.	nil
ViewsLayout	string	Views Layout is the global layout for all template render until override on Render function. See our Template Middleware for supported engines.	""
WriteBufferSize	int	Per-connection buffer size for responses' writing.	4096
WriteTimeout	time.Duration	The maximum duration before timing out writes of the response. The default timeout is unlimited.	0
XMLDecoder	utils.XMLUnmarshal	Allowing for flexibility in using another XML library for decoding.	xml.Unmarshal
XMLEncoder	utils.XMLMarshal	Allowing for flexibility in using another XML library for encoding.	xml.Marshal

Server listening

Config

You can pass an optional ListenConfig when calling the Listen or Listener method.

Example

// Custom config
app.Listen(":8080", fiber.ListenConfig{
    EnablePrefork: true,
    DisableStartupMessage: true,
})

Config fields

Property	Type	Description	Default
BeforeServeFunc	func(app *App) error	Allows customizing and accessing fiber app before serving the app.	nil
CertClientFile	string	Path of the client certificate. If you want to use mTLS, you must enter this field.	""
CertFile	string	Path of the certificate file. If you want to use TLS, you must enter this field.	""
CertKeyFile	string	Path of the certificate's private key. If you want to use TLS, you must enter this field.	""
DisableStartupMessage	bool	When set to true, it will not print out the «Fiber» ASCII art and listening address.	false
EnablePrefork	bool	When set to true, this will spawn multiple Go processes listening on the same port.	false
EnablePrintRoutes	bool	If set to true, will print all routes with their method, path, and handler.	false
GracefulContext	context.Context	Field to shutdown Fiber by given context gracefully.	nil
ShutdownTimeout	time.Duration	Specifies the maximum duration to wait for the server to gracefully shutdown. When the timeout is reached, the graceful shutdown process is interrupted and forcibly terminated, and the context.DeadlineExceeded error is passed to the OnPostShutdown callback. Set to 0 to disable the timeout and wait indefinitely.	10 * time.Second
ListenerAddrFunc	func(addr net.Addr)	Allows accessing and customizing net.Listener.	nil
ListenerNetwork	string	Known networks are "tcp", "tcp4" (IPv4-only), "tcp6" (IPv6-only), "unix" (Unix Domain Sockets). WARNING: When prefork is set to true, only "tcp4" and "tcp6" can be chosen.	tcp4
UnixSocketFileMode	os.FileMode	FileMode to set for Unix Domain Socket (ListenerNetwork must be "unix")	0770
TLSConfigFunc	func(tlsConfig *tls.Config)	Allows customizing tls.Config as you want. Ignored when TLSConfig is set.	nil
TLSConfig	*tls.Config	Recommended base TLS configuration (cloned). Use for external certificate providers via GetCertificate. When set, other TLS fields are ignored.	nil
AutoCertManager	*autocert.Manager	Manages TLS certificates automatically using the ACME protocol. Enables integration with Let's Encrypt or other ACME-compatible providers.	nil
TLSMinVersion	uint16	Allows customizing the TLS minimum version.	tls.VersionTLS12

Listen

Listen serves HTTP requests from the given address.

Signature

func (app *App) Listen(addr string, config ...ListenConfig) error

Basic Listen usage

// Listen on port :8080
app.Listen(":8080")

// Listen on port :8080 with Prefork
app.Listen(":8080", fiber.ListenConfig{EnablePrefork: true})

// Custom host
app.Listen("127.0.0.1:8080")

Prefork

Prefork is a feature that allows you to spawn multiple Go processes listening on the same port. This can be useful for scaling across multiple CPU cores.

Prefork listener

app.Listen(":8080", fiber.ListenConfig{EnablePrefork: true})

This distributes the incoming connections between the spawned processes and allows more requests to be handled simultaneously.

TLS

Prefer TLSConfig for TLS configuration so you can fully control certificates and settings. When TLSConfig is set, Fiber ignores CertFile, CertKeyFile, CertClientFile, TLSMinVersion, AutoCertManager, and TLSConfigFunc.

TLS serves HTTPs requests from the given address using certFile and keyFile paths as TLS certificate and key file.

TLS with cert and key files

app.Listen(":443", fiber.ListenConfig{CertFile: "./cert.pem", CertKeyFile: "./cert.key"})

TLS with client CA certificate

CertClientFile only configures the client CA for mTLS when using CertFile/CertKeyFile. If TLSConfig is set, CertClientFile is ignored, so configure client CAs in the provided tls.Config instead.

TLS with client CA certificate

app.Listen(":443", fiber.ListenConfig{
    CertFile:       "./cert.pem",
    CertKeyFile:    "./cert.key",
    CertClientFile: "./ca-chain-cert.pem",
})

TLS AutoCert support (ACME / Let's Encrypt)

Provides automatic access to certificates management from Let's Encrypt and any other ACME-based providers.

AutoCert (ACME) configuration

// Certificate manager
certManager := &autocert.Manager{
    Prompt: autocert.AcceptTOS,
    // Replace with your domain name
    HostPolicy: autocert.HostWhitelist("example.com"),
    // Folder to store the certificates
    Cache: autocert.DirCache("./certs"),
}

app.Listen(":444", fiber.ListenConfig{
    AutoCertManager:    certManager,
})

Precedence and conflicts

• TLSConfig is preferred and ignores CertFile/CertKeyFile, CertClientFile, AutoCertManager, TLSMinVersion, and TLSConfigFunc.
• AutoCertManager cannot be combined with CertFile/CertKeyFile.

TLS with external certificate provider

Use TLSConfig to supply a base tls.Config that can fetch certificates at runtime. TLSConfig is cloned and used as-is.

TLSConfig with dynamic certificate provider

app.Listen(":443", fiber.ListenConfig{
    TLSConfig: &tls.Config{
        GetCertificate: func(info *tls.ClientHelloInfo) (*tls.Certificate, error) {
            return myProvider.Certificate(info.ServerName)
        },
    },
})

Mutual TLS with TLSConfig

Use TLSConfig to configure mutual TLS by setting ClientAuth and ClientCAs. This replaces CertClientFile when you manage TLS configuration directly.

TLSConfig with client CA pool

certPEM := []byte(certPEMString)
keyPEM := []byte(keyPEMString)
caPEM := []byte(caPEMString)

cert, err := tls.X509KeyPair(certPEM, keyPEM)
if err != nil {
    log.Fatal(err)
}

clientCAs := x509.NewCertPool()
if ok := clientCAs.AppendCertsFromPEM(caPEM); !ok {
    log.Fatal("failed to append client CA")
}

app.Listen(":443", fiber.ListenConfig{
    TLSConfig: &tls.Config{
        Certificates: []tls.Certificate{cert},
        ClientAuth:   tls.RequireAndVerifyClientCert,
        ClientCAs:    clientCAs,
    },
})

Load certificates from memory or environment variables and provide them via TLSConfig.

TLSConfig with in-memory certificate

certPEM := []byte(certPEMString)
keyPEM := []byte(keyPEMString)

cert, err := tls.X509KeyPair(certPEM, keyPEM)
if err != nil {
    log.Fatal(err)
}

app.Listen(":443", fiber.ListenConfig{
    TLSConfig: &tls.Config{
        Certificates: []tls.Certificate{cert},
    },
})

TLSConfig with certificate from environment

certPEM := []byte(os.Getenv("TLS_CERT_PEM"))
keyPEM := []byte(os.Getenv("TLS_KEY_PEM"))

cert, err := tls.X509KeyPair(certPEM, keyPEM)
if err != nil {
    log.Fatal(err)
}

app.Listen(":443", fiber.ListenConfig{
    TLSConfig: &tls.Config{
        Certificates: []tls.Certificate{cert},
    },
})

Listener

You can pass your own net.Listener using the Listener method. This method can be used to enable TLS/HTTPS with a custom tls.Config.

Signature

func (app *App) Listener(ln net.Listener, config ...ListenConfig) error

Examples

ln, _ := net.Listen("tcp", ":3000")

cer, _:= tls.LoadX509KeyPair("server.crt", "server.key")

ln = tls.NewListener(ln, &tls.Config{Certificates: []tls.Certificate{cer}})

app.Listener(ln)

Server

Server returns the underlying fasthttp server

Signature

func (app *App) Server() *fasthttp.Server

Examples

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

    app.Server().MaxConnsPerIP = 1

    // ...
}

Server Shutdown

Shutdown gracefully shuts down the server without interrupting any active connections. Shutdown works by first closing all open listeners and then waits indefinitely for all connections to return to idle before shutting down.

ShutdownWithTimeout will forcefully close any active connections after the timeout expires.

ShutdownWithContext shuts down the server including by force if the context's deadline is exceeded. Shutdown hooks will still be executed, even if an error occurs during the shutdown process, as they are deferred to ensure cleanup happens regardless of errors.

func (app *App) Shutdown() error
func (app *App) ShutdownWithTimeout(timeout time.Duration) error
func (app *App) ShutdownWithContext(ctx context.Context) error

Helper functions

NewError

NewError creates a new HTTPError instance with an optional message.

Signature

func NewError(code int, message ...string) *Error

Example

app.Get("/", func(c fiber.Ctx) error {
    return fiber.NewError(782, "Custom error message")
})

NewErrorf

NewErrorf creates a new HTTPError instance with an optional formatted message.

Signature

func NewErrorf(code int, message ...any) *Error

Example

app.Get("/", func(c fiber.Ctx) error {
    return fiber.NewErrorf(782, "Custom error %s", "message")
})

IsChild

IsChild determines if the current process is a result of Prefork.

Signature

func IsChild() bool

Example

// Config app
app := fiber.New()

app.Get("/", func(c fiber.Ctx) error {
    if !fiber.IsChild() {
        fmt.Println("I'm the parent process")
    } else {
        fmt.Println("I'm a child process")
    }
    return c.SendString("Hello, World!")
})

// ...

// With prefork enabled, the parent process will spawn child processes
app.Listen(":8080", fiber.ListenConfig{EnablePrefork: true})