Base64 Encode Online: Text and Files in Your Browser

What the encoder does with your input

Text is converted to UTF-8 bytes first, then those bytes are encoded. This is worth knowing because encoding is defined over bytes, not characters: the same visible text in a different encoding produces a different Base64 string.

Files are read exactly as stored, with no newline translation. The output therefore matches base64 file on the command line byte for byte.

Padding, wrapping and the alphabet

Standard Base64 output has a length divisible by 4, padded with one or two = characters. Some tools strip the padding; most decoders tolerate its absence, but strict ones do not, so keep it unless a spec says otherwise.

MIME-style Base64 wraps lines at 76 characters. That breaks anything expecting a single-line value — a Kubernetes secret, an Authorization header — so this encoder emits one unbroken line, matching base64 -w 0.

If the value goes into a URL or a JWT you need base64url instead: - and _ replace + and /, and padding is normally dropped.

What encoding is not

Base64 is a transport encoding, fully reversible by anyone, with no key involved. A Base64 blob in a log file or a URL is plaintext for security purposes.

It also grows the data by about 33%, so it is a poor choice for anything large. Encode when a channel demands text — JSON, email, an env var — not as a default.