Encode

• The Clear Text (ie message to encode)

A text message with only string

• Transform the text into binary data by applying the character set table conversion
• Transform the binary into a succession of characters with the alphabet conversion table
• add the optional trailing character =
• and you get the base64 cipher

Decode

The decode steps are the same as the encode steps but in reverse. You need to use the encoded character as input.

Javascript Node

const base64 =  Buffer.from('Hello Base 64').toString('base64');

atob / btoa javascript function are deprecated.

Javascript

const base64 = window.btoa("Hello World");
console.log(`Base64: ${base64}`);
const plainText = window.atob(base64);
console.log(`Plain Text: ${plainText}`);

To decode a base64 URL encoding:

function base64Decode(s){
  // from base64 url to base 64
  s = s
       .replace(/-/g, '+')
       .replace(/_/g, '/');
  return window.atob(s);
}

See the decoder/encoder script above.

Ref:

• WebApi Ref
• Mozilla Btoa Javascript Function

base64 command utility

cat my-file | base64

Open Ssl

Openssl

echo Hello World ! | openssl base64

SGVsbG8gV29ybGQgIQo=

Java

String encode = Base64.getEncoder().encodeToString("Foo".getBytes());
byte[] decode = Base64.getDecoder().decode(encode);
System.out.println(new String(decode,StandardCharsets.UTF_8));

Foo