Glossary

Base64

Base64 is an encoding scheme that converts binary data into a string of 64 printable ASCII characters. It uses letters A–Z, a–z, digits 0–9, plus (+), and slash (/) to represent every possible byte sequence, enabling safe transmission of binary data over text-based protocols.

Base64 is an encoding scheme that converts binary data into a string of 64 printable ASCII characters. It uses letters A–Z, a–z, digits 0–9, plus (+), and slash (/) to represent every possible byte sequence, enabling safe transmission of binary data over text-based protocols like HTTP, SMTP, and XML.

How It Works

Base64 groups input bits into 6-bit chunks (since 2^6 = 64) and maps each chunk to a character in the alphabet. Three input bytes (24 bits) produce four Base64 characters. If the input does not divide evenly by three, = padding is appended.

Variants

  • Standard Base64: uses + and / as the 62nd and 63rd characters
  • URL-safe Base64: replaces + with - and / with _ for use in URLs and JWT tokens
  • MIME Base64: wraps output at 76 characters for email compatibility

Common Uses

  • HTTP Authorization: Basic header encoding
  • Data URIs for inline images in HTML/CSS
  • JWT token payload encoding
  • MIME email attachment encoding
  • Embedding binary data in JSON

Important Note

Base64 is encoding, not encryption. Anyone can decode a Base64 string instantly with no key. It provides zero security — never use Base64 to "hide" sensitive information.

Size overhead: Base64 output is approximately 33% larger than the original binary input.

Use the Base64 Encoder/Decoder Tool to encode and decode instantly in your browser.