Base64 Encoder / Decoder

The Formula

Base64 encodes binary and text data into a safe 64-character alphabet (A-Z, a-z, 0-9, +, /) for transmission over text-based protocols that might misinterpret binary data. It works by grouping input bytes into 24-bit chunks (3 bytes), splitting each chunk into four 6-bit values, and mapping each 6-bit value to one of 64 printable ASCII characters. If the input length is not a multiple of 3 bytes, = padding is added to make the output a multiple of 4 characters.

Variable Definitions

How to Use This Calculator

1. 1

   Select Encode mode to convert text to Base64, or Decode mode to convert Base64 back to plain text.

2. 2

   Enter your input text in the text area — supports plain text, numbers, and special characters.

3. 3

   The encoded or decoded output appears instantly as you type or paste.

4. 4

   Use the Copy button to copy the result to your clipboard for use in code, emails, or configuration files.

5. 5

   Character counts show the size difference: the encoded output is roughly 4/3 the size of the original due to Base64 overhead.

Base64 encodes 3 bytes into 4 ASCII characters using a 64-character alphabet, adding ~33% overhead.

Understanding the Concept

Base64 is a binary-to-text encoding scheme that represents binary data in an ASCII string format using 64 safe characters (A-Z, a-z, 0-9, +, /), with = used for padding. It is commonly used for embedding images directly in HTML or CSS as data URIs (data:image/png;base64,...), encoding email attachments via MIME, storing binary data in JSON or XML, and transmitting credentials in HTTP Basic Authentication headers. Each 3 bytes of input becomes 4 Base64 characters, adding approximately 33% overhead. Because Base64 uses only safe printable ASCII characters, it is immune to character encoding issues and transmission corruption from control characters that binary data might contain. A common variant, Base64URL, replaces + and / with - and _ and omits padding, making it safe for use in URLs and filenames.

Frequently Asked Questions

Sources & References