About this tool
The Ascii85 / Base85 tool converts binary data to and from Ascii85 (also called Base85), a text encoding that packs four bytes into five printable characters — about 25% more compact than Base64. It is used inside PostScript and PDF streams (the Adobe variant) and in patch/diff formats. Everything runs locally in your browser with TextEncoder/TextDecoder; nothing you paste is uploaded.
Encoding processes the input as 4-byte big-endian groups, reads each group as a 32-bit unsigned integer, and emits five digits by repeatedly taking the value modulo 85 and adding 33, so each digit falls in the printable range '!' (33) to 'u' (117). An all-zero group collapses to the single character 'z'. A final partial group of n bytes (1–3) is zero-padded to four, encoded, and the last 4−n output characters are dropped, yielding n+1 characters. The Adobe variant wraps the result in '<~' and '~>'.
Decoding reverses the process: whitespace and any wrapper are stripped, 'z' expands to four zero bytes, five-character groups are read as value = Σ (cᵢ−33)·85^(4−i) and written as four big-endian bytes, and a trailing partial group of m characters (2–5) is padded with 'u' (value 84) and keeps m−1 bytes. Choose the direction, the standard or Adobe variant, and whether your input bytes are UTF-8 text or hex.