Base64 Encoding Explained

What is Base64?

Base64 is a binary-to-text encoding scheme that converts binary data into a string of ASCII characters. It uses 64 characters: A-Z, a-z, 0-9, +, and /. It is used to embed binary data in text-based formats like JSON, HTML, and email.

How It Works

Every 3 bytes of input are encoded into 4 Base64 characters, increasing size by ~33%. Padding (=) is added when the input length is not a multiple of 3.

Input:   Hello
Binary:  01001000 01100101 01101100 01101100 01101111
Base64:  SGVsbG8=

Common Use Cases

• Embedding images in CSS or HTML as data URIs
• Encoding binary data in JSON API payloads
• Email attachments (MIME encoding)
• Basic HTTP authentication headers

Common Mistakes

• Using Base64 for encryption: Base64 is encoding, not encryption. Anyone can decode it.
• URL-unsafe characters: Standard Base64 uses + and / which need URL-encoding. Use Base64URL variant instead.
• Ignoring size increase: Base64 adds ~33% overhead. Don't use for large files unnecessarily.

Code Examples

// JavaScript
btoa("Hello World")     // "SGVsbG8gV29ybGQ="
atob("SGVsbG8gV29ybGQ=") // "Hello World"

// Node.js
Buffer.from("Hello").toString("base64") // "SGVsbG8="
Buffer.from("SGVsbG8=", "base64").toString() // "Hello"

Try our Base64 Encoder/Decoder to convert text or data instantly.