Base64 encoder

What Base64 is — and what it is not

Base64 is a binary-to-text encoding. Its job is to take arbitrary bytes — an image, a certificate, a token, a snippet of UTF-8 text — and re-express them using only 64 printable characters that survive channels built for plain text. Email (MIME), JSON payloads, data URIs and HTTP headers all assume text, so wrapping raw bytes in Base64 stops them from being mangled in transit. Crucially, it is not encryption: the transformation is public and reversible by anyone, so it hides nothing.

How the encoding works

The algorithm reads your input three bytes (24 bits) at a time and re-slices those 24 bits into four groups of 6 bits. Each 6-bit group has 64 possible values (2⁶), which maps neatly onto the alphabet A–Z a–z 0–9 + /. When the input length is not a multiple of three, the final group is padded and marked with = signs so the decoder knows how many real bytes to recover.

A worked example

Take the three characters Man (ASCII bytes 77, 97, 110). As 24 bits that is 01001101 01100001 01101110. Re-grouped into 6-bit chunks: 010011, 010110, 000101, 101110 = 19, 22, 5, 46 — which index to T, W, F, u. So Man encodes to TWFu. Encode just M and you get TQ==: one real byte, two padding characters.

Standard vs URL-safe vs related encodings

This tool handles the Unicode trap that breaks many encoders: before calling the browser's native encoder it converts your text to UTF-8 bytes, so emoji and non-Latin scripts decode back to exactly what you typed. Pick the URL-safe variant when the result must travel inside a URL, cookie or filename, where a stray + or / would otherwise need escaping.