Base64 encoder and decoder

Base64 represents bytes using ASCII characters so they can travel through a text field. This tool converts your text to UTF-8 before encoding it, or recovers UTF-8 text from a Base64 string. Use it for short JSON payloads, messages and integration checks. Processing takes place in your browser. It does not restore an image as a downloadable image file, and it does not protect a secret: anyone with the encoded string can reverse the operation.

Encoding uses the standard Base64 alphabet, including + and /, with = padding at the end when required. Three bytes become four characters. Long inputs therefore grow by roughly a third; for accented characters and emoji, count UTF-8 bytes rather than visible characters. Base64 is not compression and will not make a text payload smaller.

Decoding rebuilds the bytes and then requires valid UTF-8 text. A perfectly valid Base64 string may contain binary data; in that case the tool reports an error instead of silently replacing unreadable bytes. An initial byte order mark is preserved. There is no setting for Latin-1, Windows-1252 or another legacy text encoding.

The browser accepts ASCII whitespace and line breaks in the encoded input, and allows some omitted padding. This is not a strict canonical RFC 4648 validator. Base64url, which uses - and _, is unsupported. Do not include a data: prefix or paste a complete JWT: those formats have additional structure and need a different reader.