What is Base85 / Z85?

Z85 is the ZeroMQ Base85 encoding. It packs every four bytes into five printable ASCII characters using a safe 85-character alphabet, giving roughly 25 percent better density than Base64.

How does Base85 achieve better density than Base64?

Four bytes hold 4,294,967,296 possible values, and 85^5 is about 4.4 billion — just enough to cover them. So 4 bytes need only 5 characters, versus Base64 which uses about 5.3 characters for the same data.

Why is my input padded with zero bytes?

Z85 works on whole 4-byte groups. If your text length is not a multiple of four, this tool pads the end with zero bytes and tells you how many it added so encoding can complete.

Why must Z85 input be a multiple of 5 characters to decode?

Each 5-character block decodes to exactly 4 bytes. A length that is not a multiple of 5 cannot map cleanly to bytes, so the decoder reports an error.

How is Z85 different from Ascii85?

Both are Base85 family encodings, but they use different alphabets and framing. Z85 uses an 85-character set chosen to avoid quotes and backslashes, making it safe inside source code and config strings, whereas Ascii85 (PostScript/PDF) uses a different character range and z/~ markers.

Is Base85 encryption?

No. It is a reversible text encoding for binary data, not encryption. Anyone can decode it.

No. All Z85 encoding and decoding happens in your browser and your input never leaves the page.

Base85 Encoder — Gera Tools

Base85 (Z85) encoder and decoder

Base85 packs binary data more densely than Base64: every four bytes become five printable characters. This tool uses Z85, the ZeroMQ variant, whose 85-character alphabet avoids quotes and backslashes so the output is safe to embed in source code and config files.

How it works

To encode, your text is converted to UTF-8 bytes and processed in 4-byte groups. Each group is read as a 32-bit big-endian number, then expressed in base 85 as five digits, each mapped to a Z85 alphabet character. Because the encoding needs whole 4-byte groups, input whose length is not a multiple of four is padded with zero bytes (the tool reports how many). Decoding takes each 5-character block, rebuilds the 32-bit value (value = value × 85 + digit), and splits it back into 4 bytes.

Example

Encoding the 4-byte text Gera:

Gera → bytes 47 65 72 61 → m}DZH

Bytes (hex)	Z85
`47 65 72 61` (`Gera`)	`m}DZH`
`86 4F D2 6F`	`Hello` (the ZeroMQ Z85 test vector)

Everything runs in your browser — your input never leaves the page.