Base64 Text & String Encoder/Decoder
Encode plain text into standard Base64 representation or decode Base64 strings back to readable UTF-8 text.
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Last Reviewed: August 2026
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How Base64 Encoding Operates (RFC 4648 Specification)
Base64 is a binary-to-text encoding scheme defined under RFC 4648 designed to represent binary data in an ASCII string format. It is widely used across MIME email attachments, inline Data URIs in HTML/CSS, HTTP Basic Authentication headers, and JWT tokens.
The 6-Bit Encoding Mechanism
Standard ASCII characters consist of 8 bits (1 byte). Base64 converts data by taking 3 bytes (24 bits) and splitting them into 4 groups of 6 bits each (2^6 = 64 possible characters: A-Z, a-z, 0-9, +, /):
- Every 3 input bytes are divided into 4 6-bit index values.
- Each 6-bit value is mapped to its matching character in the standard 64-character alphabet table.
- If the total input bytes are not divisible by 3, padding characters (
=) are appended to complete the 4-character block.
Frequently Asked Questions (FAQ)
No! Base64 is an encoding format, not encryption. Anyone can decode a Base64 string back to plaintext without a secret key.
Base64 encoding increases data overhead by approximately 33% compared to raw binary bytes.
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