What is Base64?
Base64 is an encoding scheme that converts binary data into a text format using 64 printable ASCII characters: A-Z, a-z, 0-9, +, and /. It was designed to safely transmit binary data through systems that were designed to handle text, like email or URLs.
How Does Base64 Work?
Base64 takes 3 bytes (24 bits) of binary data at a time and converts them into 4 Base64 characters. Each Base64 character represents 6 bits of data. This means Base64-encoded data is roughly 33% larger than the original binary data.
Common Use Cases
- Embedding images in HTML/CSS — Convert images to Base64 and embed them as data URLs:
src="data:image/png;base64,..." - Email attachments — SMTP uses Base64 to encode binary attachments as text
- API authentication — HTTP Basic Auth sends credentials as Base64-encoded strings
- JWT tokens — JSON Web Tokens use Base64url encoding for their header and payload
- Data URLs — Embedding small assets directly in HTML or CSS files
Base64 vs Encryption
It is important to understand that Base64 is NOT encryption. It is just an encoding — anyone can decode Base64 text instantly. Never use Base64 to "hide" sensitive information. Use proper encryption (like AES-256) for security.
Example
The text "Hello" in Base64 is SGVsbG8=. The = sign at the end is padding to make the length a multiple of 4.
Base64 URL Variant
The standard Base64 uses + and / which are unsafe in URLs. Base64url replaces these with - and _ and omits padding. This variant is used in JWT tokens and URL-safe contexts.
Try our free Base64 Encoder/Decoder to encode and decode Base64 strings instantly in your browser.