RFC 1924 Base85 encoder & decoder

This tool applies that same alphabet and the same repeated-division algorithm to ordinary UTF-8 text: choose encode to turn a phrase into a compact Base85 string, or decode to recover the original text from a payload that uses only the RFC 1924 symbols. Characters outside the alphabet—spaces, commas, quotes, brackets, or any glyph not listed in the standard—are rejected with a clear invalid_input error that names the character and its index, so scripts never silently invent a different payload.

How to call the API and what the response contains

The default mode is encode: UTF-8 bytes of text become an RFC 1924 Base85 string. Send a JSON body with a required string field text (aliases input, value, and data) and an optional mode that is either encode or decode. Mode decode treats text as a Base85 payload and returns the recovered UTF-8 string. Input length is capped at one hundred thousand characters so a single request cannot exhaust Worker memory on pathological big-integer expansion. On success for encode, the response includes mode, input, result and base85 with the same encoded string, alphabet with the full eighty-five-character constant, alphabet_name set to rfc1924, input_bytes as the UTF-8 byte count, output_length as the encoded character count, and a short English message. On success for decode, the response includes mode, input, result and text with the decoded UTF-8 string, the same alphabet fields, input_length, output_bytes, and a matching message. Failed validation—missing text, non-string text, oversize input, an unknown mode, an invalid Base85 character, or decoded bytes that are not valid UTF-8—returns invalid_input and is never charged. Pricing is a flat $0.002 per successful request with unit item and zero marginal unit price.

Practical tips, limits, and how this differs from other bases

Round-trip checks are the fastest smoke test: encode a known phrase such as Hello World, store the result, decode it, and confirm you recover the original phrase byte-for-byte. Prefer RFC 1924 Base85 when you need the historical IPv6-compact alphabet and strict symbol validation; prefer Base64 when maximum interoperability matters more than that specific eighty-five-symbol set. When teaching, show the same sentence under Base85, Base58, and Base64 so learners see how alphabet choice changes density, readability, and which characters are legal. Deliberately include a forbidden character—a space, comma, quote, or colon—in a decode request to assert that your client handles invalid_input and the error message that names the index. Keep payloads under the published character limit; extremely long strings expand as big integers and are better split or handled offline. This tool is not an IPv6 presentation-format parser: it does not expand compressed colon-hex, insert zone indices, or enforce twenty-digit fixed width for 128-bit addresses unless your caller pads and interprets that way. It is also not Adobe Ascii85 or ZeroMQ Z85—those use different symbol orderings and framing rules. Failed tasks that return invalid_input do not consume prepaid balance, which keeps exploratory scripts cheap when you fuzz invalid alphabet characters.