What Is Base64 Encoding?

Base64 is a binary-to-text encoding scheme that represents binary data using 64 ASCII characters: uppercase A–Z, lowercase a–z, digits 0–9, plus + and /, with = as padding.

It was designed to safely transmit binary data (images, files, audio) through systems that only handle text — like email, HTTP headers, or XML.

Why Is Base64 Used?

  • Email attachments — MIME encoding embeds binary attachments as Base64 text.
  • Data URLs — Embed images directly in HTML/CSS: src="data:image/png;base64,..."
  • API tokens — Basic Auth credentials are Base64-encoded: Authorization: Basic dXNlcjpwYXNz
  • JSON payloads — Binary data in JSON must be Base64-encoded since JSON is text-only.
  • Cookies and sessions — Store binary session data as text-safe strings.

Base64 Encoding vs Encryption — A Critical Distinction

⚠️ Base64 is NOT encryption. It provides zero security — anyone can decode it instantly. It's simply a way to represent binary data as text. Never use Base64 to "hide" passwords or sensitive data.

How to Encode/Decode Base64 Online

  1. Visit FavorTool Base64 Encoder.
  2. Paste your text in the input field.
  3. Click Encode to convert to Base64 or Decode to reverse it.
  4. Copy the result with one click.

Base64 URL Variant

Standard Base64 uses + and / which have special meaning in URLs. The URL-safe Base64 variant replaces them with - and _, and omits padding. This is used in JWTs (JSON Web Tokens) and OAuth tokens.

Base64 Encoding Size Overhead

Base64 encoding increases data size by approximately 33%. A 100-byte binary file becomes ~133 bytes when Base64-encoded. This overhead is the trade-off for text compatibility.

Common Base64 Strings You'll See

// "Hello, World!" encoded
SGVsbG8sIFdvcmxkIQ==

// JWT header (Base64URL)
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9

// Small PNG pixel (Data URL)
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJ...