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About Ascii85 (Base85) Encoder & Decoder Online
Ascii85, also called Base85, is a binary-to-text encoding that packs every 4 bytes of data into 5 printable ASCII characters. It was popularised by Adobe's PostScript and PDF formats, where it stores image and stream data as text. Because it uses an 85-character alphabet instead of 64, Ascii85 is roughly 20% more compact than Base64 — a meaningful saving inside large documents.
This free Ascii85 encoder and decoder converts UTF-8 text in both directions right in your browser. It understands the standard <~ … ~> delimiters and the "z" shorthand for all-zero groups, and tolerates the line wrapping you find in real PDF streams. Nothing you paste is ever uploaded — all work happens offline on your device.
Features
- Encode UTF-8 text to Ascii85/Base85 and decode it back
- Standard <~ ~> delimiters added on encode, optional on decode
- Supports the "z" zero-group shorthand and ignores embedded whitespace
- About 20% more compact than Base64; runs completely offline
How to use
- Paste your text or an Ascii85 string into the input pane.
- Choose Encode to convert text → Ascii85, or Decode for the reverse.
- Copy the result from the output pane — or clear and start again.
Frequently asked questions
What is the difference between Ascii85 and Base64?
Both turn binary data into text, but Ascii85 maps 4 bytes to 5 characters (an 85-symbol alphabet) while Base64 maps 3 bytes to 4 characters (64 symbols). Ascii85 output is therefore about 20% smaller, at the cost of using more punctuation characters.
What do the <~ and ~> markers mean?
They are the standard Adobe framing that marks the start and end of an Ascii85 stream. This tool adds them automatically when encoding. When decoding, they are optional — paste a string with or without them and it still works.
What is the "z" character for?
It is a shorthand: a single "z" stands in for a full group of four zero bytes, which would otherwise encode as five "!" characters. It keeps runs of zeros compact and is only valid for complete 4-byte groups.
Does Ascii85 secure or compress my data?
Neither in a cryptographic sense. Ascii85 is a reversible text encoding, so it offers no confidentiality — anyone can decode it. It does shrink the text overhead versus Base64, but it makes the data slightly larger than the raw bytes; it is a transport format, not a cipher or a compressor.
Where is my pasted text processed?
Entirely on your own machine. The Ascii85 conversion runs in JavaScript inside this page using the browser TextEncoder and TextDecoder, with no network request, so PDF streams or private payloads never travel to a server.
Related tools
Everything runs locally in your browser — your input is never uploaded.