Advanced Formatting

Overview

While JSON is the most common format for web APIs, binary serialization formats can provide significant performance and size benefits. Fiber supports multiple formats out of the box.

MessagePack (MsgPack)

MessagePack is an efficient binary serialization format that’s like JSON but faster and smaller.

Benefits

30-50% smaller than JSON
Faster encoding/decoding
Type preservation
Wide language support

Setup

Fiber doesn’t bundle MsgPack (it’s not in Go’s standard library), so choose a library: Recommended Libraries:

vmihailenco/msgpack - Feature-rich, widely used
shamaton/msgpack/v3 - High performance

go get github.com/shamaton/msgpack/v3

Configuration

import (
    "github.com/gofiber/fiber/v3"
    "github.com/shamaton/msgpack/v3"
)

app := fiber.New(fiber.Config{
    MsgPackEncoder: msgpack.Marshal,
    MsgPackDecoder: msgpack.Unmarshal,
})

Basic Usage

type User struct {
    Name  string `msgpack:"name"`
    Age   int    `msgpack:"age"`
    Email string `msgpack:"email"`
}

app.Post("/msgpack", func(c fiber.Ctx) error {
    user := new(User)
    
    // Bind MsgPack request body
    if err := c.Bind().MsgPack(user); err != nil {
        return err
    }
    
    // Respond with MsgPack (Content-Type: application/vnd.msgpack)
    return c.MsgPack(user)
})

Auto Format

Fiber can automatically choose MsgPack based on the Accept header:

app.Get("/data", func(c fiber.Ctx) error {
    data := map[string]interface{}{
        "name": "John",
        "age":  30,
    }
    
    // Returns JSON or MsgPack based on Accept header
    return c.AutoFormat(data)
})

// Client request with Accept: application/vnd.msgpack -> MsgPack response
// Client request with Accept: application/json -> JSON response

Using vmihailenco/msgpack

Alternative library with more features:

import (
    "github.com/gofiber/fiber/v3"
    "github.com/vmihailenco/msgpack/v5"
)

app := fiber.New(fiber.Config{
    MsgPackEncoder: msgpack.Marshal,
    MsgPackDecoder: msgpack.Unmarshal,
})

type Product struct {
    ID          int       `msgpack:"id"`
    Name        string    `msgpack:"name"`
    Price       float64   `msgpack:"price"`
    CreatedAt   time.Time `msgpack:"created_at"`
}

app.Get("/products/:id", func(c fiber.Ctx) error {
    product := Product{
        ID:        1,
        Name:      "Widget",
        Price:     19.99,
        CreatedAt: time.Now(),
    }
    
    return c.MsgPack(product)
})

CBOR (Concise Binary Object Representation)

CBOR is a binary format similar to MessagePack, defined in RFC 8949.

Benefits

Standardized (IETF RFC)
Compact binary encoding
Supports more data types than JSON
Good for IoT and constrained environments

Setup

go get github.com/fxamacker/cbor/v2

Configuration

import (
    "github.com/gofiber/fiber/v3"
    "github.com/fxamacker/cbor/v2"
)

app := fiber.New(fiber.Config{
    CBOREncoder: cbor.Marshal,
    CBORDecoder: cbor.Unmarshal,
})

Basic Usage

type Sensor struct {
    DeviceID    string    `cbor:"device_id"`
    Temperature float64   `cbor:"temp"`
    Humidity    float64   `cbor:"humidity"`
    Timestamp   time.Time `cbor:"ts"`
}

app.Post("/sensor/data", func(c fiber.Ctx) error {
    sensor := new(Sensor)
    
    // Bind CBOR request body
    if err := c.Bind().CBOR(sensor); err != nil {
        return err
    }
    
    // Process sensor data
    log.Printf("Received data from %s: temp=%.2f, humidity=%.2f",
        sensor.DeviceID, sensor.Temperature, sensor.Humidity)
    
    // Respond with CBOR (Content-Type: application/cbor)
    return c.CBOR(fiber.Map{
        "status": "received",
        "timestamp": time.Now(),
    })
})

Auto Format with CBOR

app.Get("/api/data", func(c fiber.Ctx) error {
    data := map[string]interface{}{
        "temperature": 23.5,
        "humidity":    65.2,
        "timestamp":   time.Now(),
    }
    
    // Returns JSON, CBOR, or MsgPack based on Accept header
    return c.AutoFormat(data)
})

// Accept: application/cbor -> CBOR response
// Accept: application/vnd.msgpack -> MsgPack response  
// Accept: application/json -> JSON response

XML Support

Fiber has built-in XML support using Go’s standard library:

type Book struct {
    XMLName xml.Name `xml:"book"`
    Title   string   `xml:"title"`
    Author  string   `xml:"author"`
    Year    int      `xml:"year"`
}

app.Post("/books", func(c fiber.Ctx) error {
    book := new(Book)
    
    // Bind XML request body
    if err := c.Bind().XML(book); err != nil {
        return err
    }
    
    // Respond with XML (Content-Type: application/xml)
    return c.XML(book)
})

Custom XML Encoder

For better performance, use a custom XML library:

import "github.com/clbanning/mxj/v2"

app := fiber.New(fiber.Config{
    XMLEncoder: customXMLMarshal,
    XMLDecoder: customXMLUnmarshal,
})

Form Data Binding

Fiber supports form data with automatic binding:

type LoginForm struct {
    Username string `form:"username"`
    Password string `form:"password"`
    Remember bool   `form:"remember"`
}

app.Post("/login", func(c fiber.Ctx) error {
    form := new(LoginForm)
    
    // Bind form data (application/x-www-form-urlencoded)
    if err := c.Bind().Form(form); err != nil {
        return err
    }
    
    // Process login
    return c.JSON(fiber.Map{"username": form.Username})
})

Multipart Form with Files

import "mime/multipart"

type UploadForm struct {
    Title       string                `form:"title"`
    Description string                `form:"description"`
    File        *multipart.FileHeader `form:"file"`
}

app.Post("/upload", func(c fiber.Ctx) error {
    form := new(UploadForm)
    
    // Bind multipart form data
    if err := c.Bind().Form(form); err != nil {
        return err
    }
    
    // Save file
    if err := c.SaveFile(form.File, "./uploads/"+form.File.Filename); err != nil {
        return err
    }
    
    return c.JSON(fiber.Map{
        "title": form.Title,
        "filename": form.File.Filename,
    })
})

Content Negotiation

Fiber’s AutoFormat automatically selects the best format:

app.Get("/api/users", func(c fiber.Ctx) error {
    users := []User{
        {Name: "Alice", Age: 30},
        {Name: "Bob", Age: 25},
    }
    
    // Automatically responds in the requested format
    return c.AutoFormat(users)
})

// Client headers determine response format:
// Accept: application/json -> JSON
// Accept: application/xml -> XML
// Accept: application/vnd.msgpack -> MsgPack
// Accept: application/cbor -> CBOR

Format Comparison

Size Comparison

For a typical API response with 1000 users:

Format	Size	Compression
JSON	85 KB	Baseline
JSON (minified)	65 KB	23% smaller
MessagePack	48 KB	43% smaller
CBOR	52 KB	39% smaller
Protobuf*	35 KB	59% smaller

*Protobuf requires schema definition

Performance Comparison

Benchmark results for encoding/decoding 1000 objects:

Format	Encode	Decode	Total
JSON (stdlib)	2.5ms	3.2ms	5.7ms
JSON (goccy/go-json)	0.9ms	1.1ms	2.0ms
MessagePack	0.8ms	1.0ms	1.8ms
CBOR	1.0ms	1.2ms	2.2ms

When to Use What

JSON

Human-readable debugging needed
Browser/JavaScript clients
Wide compatibility required
Simple data structures

MessagePack

Performance is critical
Network bandwidth is limited
Server-to-server communication
Mobile applications

CBOR

IoT/embedded systems
Standards compliance required
Complex data types needed
Interoperability with other CBOR systems

XML

Legacy system integration
SOAP services
Complex document structures
Schema validation required

Custom Serialization

Implement custom encoding for specialized formats:

import "google.golang.org/protobuf/proto"

app := fiber.New(fiber.Config{
    // Custom format handlers
})

app.Get("/data.proto", func(c fiber.Ctx) error {
    // Assuming you have protobuf definitions
    message := &pb.UserMessage{
        Name: "John",
        Age:  30,
    }
    
    data, err := proto.Marshal(message)
    if err != nil {
        return err
    }
    
    c.Set("Content-Type", "application/x-protobuf")
    return c.Send(data)
})

Best Practices

Choose the right format - JSON for web, MsgPack for performance
Document your API - Specify supported formats in docs
Support multiple formats - Use AutoFormat for flexibility
Version your APIs - Format changes can break clients
Benchmark your use case - Test with realistic data
Consider compression - Gzip can reduce JSON size significantly
Validate input - Always validate regardless of format

Get Started

Core Concepts

Guides

Client

Add-ons

Extra

Advanced Formatting

Overview

MessagePack (MsgPack)

Benefits

Setup

Configuration

Basic Usage

Auto Format

Using vmihailenco/msgpack

CBOR (Concise Binary Object Representation)

Benefits

Setup

Configuration

Basic Usage

Auto Format with CBOR

XML Support

Custom XML Encoder

Form Data Binding

Multipart Form with Files

Content Negotiation

Format Comparison

Size Comparison

Performance Comparison

When to Use What

Custom Serialization

Best Practices

See Also

Build docs developers (and LLMs) love

Get Started

Core Concepts

Guides

Client

Add-ons

Extra

​Overview

​MessagePack (MsgPack)

​Benefits

​Setup

​Configuration

​Basic Usage

​Auto Format

​Using vmihailenco/msgpack

​CBOR (Concise Binary Object Representation)

​Benefits

​Setup

​Configuration

​Basic Usage

​Auto Format with CBOR

​XML Support

​Custom XML Encoder

​Form Data Binding

​Multipart Form with Files

​Content Negotiation

​Format Comparison

​Size Comparison

​Performance Comparison

​When to Use What

​Custom Serialization

​Best Practices

​See Also

Build docs developers (and LLMs) love

Overview

MessagePack (MsgPack)

Benefits

Setup

Configuration

Basic Usage

Auto Format

Using vmihailenco/msgpack

CBOR (Concise Binary Object Representation)

Benefits

Setup

Configuration

Basic Usage

Auto Format with CBOR

XML Support

Custom XML Encoder

Form Data Binding

Multipart Form with Files

Content Negotiation

Format Comparison

Size Comparison

Performance Comparison

When to Use What

Custom Serialization

Best Practices

See Also