Base85 (Ascii85) decode
Base85 (Ascii85) decode. Runs on your device, nothing is uploaded.
Base85 (Ascii85) decode strips a leading <~ and trailing ~> wrapper when present. It then reads five characters at a time into four bytes, a lone z standing for four zero bytes. A leftover group under two characters, or an out-of-range character, is refused with its offset. A short final group of n characters yields n minus 1 bytes.
Questions
Does it accept the <~ ~> wrapper?
Yes, a leading <~ and trailing ~> are stripped if present, matching Adobe's Ascii85 convention.
What does the z shortcut mean?
A lone z in the input expands to four zero bytes, the standard Ascii85 shorthand for an all-zero group.
How does a short final group work?
A leftover group of n characters, at least 2, decodes to n minus 1 bytes.
What happens with fewer than 2 leftover characters?
The tool refuses, since a group needs at least 2 characters to resolve to a byte.
Can I use this from the command line?
Yes, the same code runs on the page, the CLI and MCP.