Base64: what is it and why is it needed?

What is Base64?

Base64 is a way of encoding binary data (bytes) into text format using 64 characters: A-Z, a-z, 0-9, +, /.

Why do you need Base64?

- Email attachments - MIME protocol uses Base64 for files

- Data URI — embedding images directly into HTML/CSS

- JWT tokens - header and payload are encoded in Base64

- API requests — transfer of binary data to JSON

- HTTP Basic Auth — Authorization: Basic dXNlcjpwYXNz

Example in JavaScript

// Encoding 
const encoded = btoa(''Hello, World!''); // "SGVsbG8sIFdvcmxkIQ==" 

// Decoding 
const decoded = atob(''SGVsbG8sIFdvcmxkIQ==''); // "Hello, World!" 

// For UTF-8 (Cyrillic, etc.) 
const encodeUTF8 = str ='>' btoa(unescape(encodeURIComponent(str))); 
const decodeUTF8 = str ='>' decodeURIComponent(escape(atob(str))); 

Data size

Base64 increases the data size by approximately 33%: every 3 bytes becomes 4 characters.

Try our free Base64 encoder - supports UTF-8 and Cyrillic.