Base64 Encode Guide

What is Base64 Encoding?

Base64 encoding converts binary data into ASCII text format using 64 printable characters (A-Z, a-z, 0-9, +, /). It's widely used for transmitting binary data over text-based protocols like email, JSON, and XML.

How Base64 Encoding Works

Base64 encoding converts every 3 bytes (24 bits) of binary data into 4 ASCII characters:

1. Takes 3 bytes (24 bits) of input
2. Splits into 4 groups of 6 bits each
3. Maps each 6-bit group to a Base64 character
4. Adds padding (=) if needed to make output length a multiple of 4

Examples

Basic Text Encoding

Email Address

Special Characters

Common Use Cases

1. Email Attachments

Email protocols (SMTP) only support ASCII text. Base64 encoding allows binary files to be sent as text:

Content-Type: image/png; name="logo.png"
Content-Transfer-Encoding: base64

iVBORw0KGgoAAAANSUhEUgAAAAUA...

2. Data URIs in HTML/CSS

Embed images directly in HTML or CSS without separate files:

<img src="data:image/png;base64,iVBORw0KGgo..." />

.logo {
  background-image: url('data:image/svg+xml;base64,PHN2Zy...');
}

3. API Authentication

HTTP Basic Authentication uses Base64 to encode credentials:

// Encode username:password
const credentials = btoa('username:password');
// Result: dXNlcm5hbWU6cGFzc3dvcmQ=

// HTTP header
Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=

4. JSON Data Transmission

Send binary data in JSON format:

{
  "filename": "document.pdf",
  "content": "JVBERi0xLjQKJeLjz9MKMSAwIG9iago8P..."
}

5. Storing Binary in Databases

Store images or files in text-based database fields:

INSERT INTO files (name, data) 
VALUES ('avatar.png', 'iVBORw0KGgoAAAANSUhEU...');

Programming Examples

JavaScript

// Browser (built-in)
const encoded = btoa('Hello World');
console.log(encoded); // SGVsbG8gV29ybGQ=

// Node.js
const encoded = Buffer.from('Hello World').toString('base64');
console.log(encoded); // SGVsbG8gV29ybGQ=

Python

import base64

text = "Hello World"
encoded = base64.b64encode(text.encode('utf-8'))
print(encoded.decode('utf-8'))  # SGVsbG8gV29ybGQ=

PHP

$text = "Hello World";
$encoded = base64_encode($text);
echo $encoded;  // SGVsbG8gV29ybGQ=

Important Notes

Size Increase

Base64 encoding increases data size by approximately 33% because it converts 3 bytes into 4 characters.

• Original: 3 bytes = 24 bits
• Encoded: 4 characters = 32 bits
• Overhead: 33% increase

Best Practices

1. Use for text protocols: Ideal when transmitting binary over text-based systems
2. Consider alternatives: For large files, direct binary transfer may be more efficient
3. Handle padding: Ensure proper = padding for compatibility
4. UTF-8 encoding: Always encode text as UTF-8 before Base64 encoding
5. URL-safe variant: Use Base64url for URLs (replaces + with - and / with _)

Try It Yourself

Use our free Base64 encoder to convert your text instantly:

Related Encoding Tools

• Base64 Decode - Decode Base64 back to text
• URL Encode - Encode text for URLs
• HTML Entity Encode - Encode HTML special characters