Base64 Encoding & Decoding Code Examples

// Browser / Node.js 16+
const encoded = btoa('Hello, World!');
console.log(encoded); // "SGVsbG8sIFdvcmxkIQ=="

// For Unicode strings, encode to UTF-8 first
function toBase64(str) {
  return btoa(unescape(encodeURIComponent(str)));
}
console.log(toBase64('Привет')); // "0J/RgNC40LLQtdGC"

const decoded = atob('SGVsbG8sIFdvcmxkIQ==');
console.log(decoded); // "Hello, World!"

// For Unicode strings
function fromBase64(b64) {
  return decodeURIComponent(escape(atob(b64)));
}
console.log(fromBase64('0J/RgNC40LLQtdGC')); // "Привет"

import base64

# Encode a string
encoded = base64.b64encode(b'Hello, World!').decode('utf-8')
print(encoded)  # "SGVsbG8sIFdvcmxkIQ=="

# Encode from a variable
text = "Hello, World!"
encoded = base64.b64encode(text.encode('utf-8')).decode('utf-8')
print(encoded)  # "SGVsbG8sIFdvcmxkIQ=="

import base64

encoded = 'SGVsbG8sIFdvcmxkIQ=='
decoded = base64.b64decode(encoded).decode('utf-8')
print(decoded)  # "Hello, World!"

# URL-safe Base64
url_safe = base64.urlsafe_b64encode(b'data with +/=').decode()
print(url_safe)  # Uses - and _ instead of + and /

<?php
$encoded = base64_encode('Hello, World!');
echo $encoded; // "SGVsbG8sIFdvcmxkIQ=="

// Encode binary data (e.g., file contents)
$fileData = file_get_contents('image.png');
$base64Image = base64_encode($fileData);
echo 'data:image/png;base64,' . $base64Image;

<?php
$decoded = base64_decode('SGVsbG8sIFdvcmxkIQ==');
echo $decoded; // "Hello, World!"

// With strict mode (returns false on invalid input)
$result = base64_decode('invalid!@#', true);
if ($result === false) {
    echo "Invalid Base64 input";
}

package main

import (
    "encoding/base64"
    "fmt"
)

func main() {
    data := "Hello, World!"

    // Standard encoding
    encoded := base64.StdEncoding.EncodeToString([]byte(data))
    fmt.Println(encoded) // "SGVsbG8sIFdvcmxkIQ=="

    // URL-safe encoding
    urlEncoded := base64.URLEncoding.EncodeToString([]byte(data))
    fmt.Println(urlEncoded)
}

package main

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

func main() {
    encoded := "SGVsbG8sIFdvcmxkIQ=="
    decoded, err := base64.StdEncoding.DecodeString(encoded)
    if err != nil {
        log.Fatal("Decode error:", err)
    }
    fmt.Println(string(decoded)) // "Hello, World!"
}

import java.util.Base64;
import java.nio.charset.StandardCharsets;

public class Base64Example {
    public static void main(String[] args) {
        String text = "Hello, World!";

        // Encode
        String encoded = Base64.getEncoder()
            .encodeToString(text.getBytes(StandardCharsets.UTF_8));
        System.out.println(encoded); // "SGVsbG8sIFdvcmxkIQ=="

        // URL-safe encoding
        String urlSafe = Base64.getUrlEncoder()
            .encodeToString(text.getBytes(StandardCharsets.UTF_8));
    }
}

import java.util.Base64;
import java.nio.charset.StandardCharsets;

String encoded = "SGVsbG8sIFdvcmxkIQ==";
byte[] decodedBytes = Base64.getDecoder().decode(encoded);
String decoded = new String(decodedBytes, StandardCharsets.UTF_8);
System.out.println(decoded); // "Hello, World!"

// Cargo.toml: base64 = "0.22"
use base64::{Engine as _, engine::general_purpose};

fn main() {
    let data = "Hello, World!";
    let encoded = general_purpose::STANDARD.encode(data);
    println!("{}", encoded); // "SGVsbG8sIFdvcmxkIQ=="

    // URL-safe encoding
    let url_safe = general_purpose::URL_SAFE.encode(data);
    println!("{}", url_safe);
}

use base64::{Engine as _, engine::general_purpose};

fn main() {
    let encoded = "SGVsbG8sIFdvcmxkIQ==";
    match general_purpose::STANDARD.decode(encoded) {
        Ok(bytes) => {
            let text = String::from_utf8(bytes).unwrap();
            println!("{}", text); // "Hello, World!"
        }
        Err(e) => eprintln!("Decode error: {}", e),
    }
}

using System;
using System.Text;

string text = "Hello, World!";
byte[] bytes = Encoding.UTF8.GetBytes(text);
string encoded = Convert.ToBase64String(bytes);
Console.WriteLine(encoded); // "SGVsbG8sIFdvcmxkIQ=="

using System;
using System.Text;

string encoded = "SGVsbG8sIFdvcmxkIQ==";
byte[] bytes = Convert.FromBase64String(encoded);
string decoded = Encoding.UTF8.GetString(bytes);
Console.WriteLine(decoded); // "Hello, World!"

require 'base64'

# Encode
encoded = Base64.strict_encode64('Hello, World!')
puts encoded  # "SGVsbG8sIFdvcmxkIQ=="

# Decode
decoded = Base64.strict_decode64('SGVsbG8sIFdvcmxkIQ==')
puts decoded  # "Hello, World!"

# URL-safe variant
url_safe = Base64.urlsafe_encode64('data with +/=')
puts url_safe  # Uses - and _ instead of + and /

# Encode a string
echo -n "Hello, World!" | base64
# Output: SGVsbG8sIFdvcmxkIQ==

# Decode a string
echo "SGVsbG8sIFdvcmxkIQ==" | base64 --decode
# Output: Hello, World!

# Encode a file
base64 < input.txt > encoded.txt

# Decode a file
base64 --decode < encoded.txt > output.txt