Skip to main content
Go provides built-in support for base64 encoding/decoding.

​
Standard Base64 Encoding

Import the package with an alias to save space: 
import (
    b64 "encoding/base64"
    "fmt"
)

data := "abc123!?$*&()'-=@~"

​
Encoding

The encoder requires a []byte, so convert your string: 
sEnc := b64.StdEncoding.EncodeToString([]byte(data))
fmt.Println(sEnc)
// Output: YWJjMTIzIT8kKiYoKSctPUB+

​
Decoding

Decoding may return an error if the input is malformed: 
sDec, _ := b64.StdEncoding.DecodeString(sEnc)
fmt.Println(string(sDec))
// Output: abc123!?$*&()'-=@~
Always check the error when decoding Base64 data, especially from untrusted sources.

​
URL-Compatible Base64

For URL-safe encoding, use URLEncoding: 
uEnc := b64.URLEncoding.EncodeToString([]byte(data))
fmt.Println(uEnc)
// Output: YWJjMTIzIT8kKiYoKSctPUB-

uDec, _ := b64.URLEncoding.DecodeString(uEnc)
fmt.Println(string(uDec))
// Output: abc123!?$*&()'-=@~
URL encoding uses - and _ instead of + and / to avoid URL encoding issues.

​
Encoding Types

Uses + and / characters, suitable for most uses
Uses - and _ characters, safe for URLs and filenames
Standard encoding without padding = characters
URL encoding without padding = characters

​
Encoding Functions

​
EncodeToString
func(src []byte) string
Encodes bytes to a Base64 string
​
DecodeString
func(s string) ([]byte, error)
Decodes a Base64 string to bytes
​
Encode
func(dst, src []byte)
Encodes bytes to Base64 bytes
​
Decode
func(dst, src []byte) (n int, err error)
Decodes Base64 bytes to bytes

​
Working with Readers and Writers

For streaming operations, use encoders and decoders: 
import (
    "encoding/base64"
    "os"
)

// Encode to stdout
encoder := base64.NewEncoder(base64.StdEncoding, os.Stdout)
encoder.Write([]byte("data to encode"))
encoder.Close()

// Decode from stdin
decoder := base64.NewDecoder(base64.StdEncoding, os.Stdin)
decodedData, _ := io.ReadAll(decoder)

​
Use Cases

Binary Data

Embed binary data in text formats

APIs

Transfer binary data in JSON/XML

Email

Encode attachments in MIME

Data URIs

Embed images in HTML/CSS

​
Example: Image Data URI

import (
    "encoding/base64"
    "fmt"
    "os"
)

data, _ := os.ReadFile("image.png")
encoded := base64.StdEncoding.EncodeToString(data)

dataURI := fmt.Sprintf("data:image/png;base64,%s", encoded)
fmt.Println(dataURI)

​
Package Reference

Build docs developers (and LLMs) love

Get started for freeTalk to us