Base91 Encoder Decoder

basE91 is a binary-to-text encoding designed by Joachim Henke that squeezes roughly 23% more data into each character than Base64.

It does this by emitting 13 or 14 bits at a time across pairs of symbols drawn from a 91-character alphabet, so the same payload produces a shorter, denser string.

That makes it a neat choice when you need ASCII-safe text but want to waste fewer bytes — embedding small binary blobs in configuration files, log lines, query strings or anywhere overhead matters.

This tool encodes any UTF-8 text into basE91 and decodes a basE91 string back to the original text.

Encoding always succeeds; decoding validates every character against the alphabet and reports the first offending symbol, then checks that the recovered bytes form valid UTF-8 so you know immediately if the input was corrupted.

Whitespace and line breaks pasted from a wrapped block are ignored on decode, which makes copy-and-paste painless.

The alphabet deliberately omits the apostrophe, hyphen and backslash, so output stays safe inside double-quoted strings.

Everything runs locally in your browser — nothing is uploaded, logged or stored — so it is safe for private data and keeps working offline once the page has loaded.