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Base64 Encoder & Decoder

Encode strings to RFC 4648 Base64 or decode Base64 data to plain text instantly in your browser.

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About this Base64 Encoder & Decoder

The Base64 Encoder & Decoder converts ASCII and binary data into 64-character radix text streams based on RFC 4648 standards for safe transmission in JSON, email, and URLs.

Transparent calculation methodology
Editorial review: CalculatorAll.online Editorial TeamLast reviewed: August 29, 2026

How this calculation works

The Base64 Encoder & Decoder converts ASCII and binary data into 64-character radix text streams based on RFC 4648 standards for safe transmission in JSON, email, and URLs.

Mathematical formula and logic

Base64 converts 3 bytes (24 bits) into 4 characters (6 bits each), resulting in a ~33% size overhead.

Worked example

'Hello World! CalculatorAll 2026' encodes to 'SGVsbG8gV29ybGQhIENhbGN1bGF0b3JBbGwgMjAyNg=='.

Calculation assumptions

  • RFC 4648 standard Base64 character set (A-Z, a-z, 0-9, +, /) with '=' padding.
  • Input is treated as UTF-8 encoded text.

Frequently asked questions

What is Base64 encoding used for?

Base64 encoding is used to transmit binary data (like images, tokens, and cryptographic keys) across text-based network protocols (like HTTP headers, JSON, and HTML) without data corruption.

Is Base64 encryption?

No, Base64 is an encoding format, not encryption. Anyone can decode a Base64 string instantly back into its original form without a key.

Why does Base64 increase file size by 33%?

Base64 maps 3 bytes of binary data (24 bits) into 4 printable ASCII characters (6 bits each), expanding data volume by exactly 4/3 (~33.3%).

What is URL-safe Base64?

URL-safe Base64 replaces '+' with '-' and '/' with '_' so the encoded string can be included in URL query parameters without percent-encoding.

What is the '=' character at the end of Base64?

The '=' symbol is padding used to ensure the encoded string's length is a multiple of 4 when input byte length is not divisible by 3.