Go Academy · Lesson

gob and Binary Encoding

Encode Go values.

gob and Binary Encoding is a free Go Academy lesson on CoddyKit — lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Go Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What Is gob

encoding/gob is a Go-specific binary format for serializing Go values. It is compact and fast, ideal for Go-to-Go communication and on-disk storage.

gob vs JSON

JSON is text, human-readable, and cross-language. gob is binary, Go-only, but more compact and faster to encode. Use gob when both ends are Go programs.

Encoding to a Buffer

A gob.Encoder writes to any io.Writer. Here we use a bytes.Buffer to hold the binary output.

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
)

func main() {
	var buf bytes.Buffer
	enc := gob.NewEncoder(&buf)
	enc.Encode(42)
	fmt.Println("bytes written:", buf.Len())
}

Decoding from a Buffer

A gob.Decoder reads from an io.Reader and fills a pointer, just like Unmarshal.

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
)

func main() {
	var buf bytes.Buffer
	gob.NewEncoder(&buf).Encode(42)
	var n int
	gob.NewDecoder(&buf).Decode(&n)
	fmt.Println(n)
}

Encoding Structs

gob handles structs naturally. Only exported fields are encoded.

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
)

type User struct {
	Name string
	Age  int
}

func main() {
	var buf bytes.Buffer
	gob.NewEncoder(&buf).Encode(User{"Ann", 30})
	var u User
	gob.NewDecoder(&buf).Decode(&u)
	fmt.Println(u)
}

Encoding Maps and Slices

Composite types like maps and slices encode and decode transparently.

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
)

func main() {
	var buf bytes.Buffer
	gob.NewEncoder(&buf).Encode([]int{1, 2, 3})
	var s []int
	gob.NewDecoder(&buf).Decode(&s)
	fmt.Println(s)
}

Self-Describing Streams

gob streams include type information, so the decoder can rebuild values even mapping to a slightly different but compatible struct. Extra or missing fields are tolerated.

Exported Fields Only

Like JSON, gob only encodes exported fields. Unexported (lowercase) fields are skipped silently.

package main

import (
	"bytes"
	"encoding/gob"
	"fmt"
)

type T struct {
	Public  int
	private int
}

func main() {
	var buf bytes.Buffer
	gob.NewEncoder(&buf).Encode(T{Public: 1, private: 2})
	var out T
	gob.NewDecoder(&buf).Decode(&out)
	fmt.Println(out.Public, out.private)
}

Other Binary Options

For raw fixed-size binary, encoding/binary writes integers and floats in big or little endian. It is lower level than gob and not self-describing.

package main

import (
	"bytes"
	"encoding/binary"
	"fmt"
)

func main() {
	var buf bytes.Buffer
	binary.Write(&buf, binary.BigEndian, uint32(258))
	fmt.Println(buf.Bytes())
}

When to Use Each

Choose:

json - APIs, config, cross-language
gob - Go-to-Go, compact, easy with structs
binary - exact byte layouts, protocols

Not Human Readable

gob output is binary; printing it shows gibberish. That is the tradeoff for compactness. Use it for machines, not logs you read.

Quick Check

When is gob a better choice than JSON?

Recap

gob and binary encoding:

gob.NewEncoder/NewDecoder for Go-to-Go binary
Compact, self-describing, exported fields only
encoding/binary for exact byte layouts
JSON remains best for cross-language and readability

Frequently asked questions

Is the “gob and Binary Encoding” lesson free?

Yes — the full text of “gob and Binary Encoding” is free to read here on the web, and the Go Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Go Academy course, upgrade to CoddyKit PRO.

What will I learn in “gob and Binary Encoding”?

Encode Go values. You practise Go Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Go Academy?

No prior experience is required. Go Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 4 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “gob and Binary Encoding” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Go Academy lesson?

Yes. Every Go Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

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