Question 1

How is Base85 different from Base64, and when is it worth using?

Accepted Answer

Base64 turns 3 bytes into 4 characters, a 33% size increase. Base85 turns 4 bytes into 5 characters, only about 25% overhead, because 85^5 (4.4 billion) is just big enough to hold every 32-bit value (4.29 billion). So encoding the same 1 KB blob, Base64 gives ~1366 chars and Base85 gives ~1280. That margin is why Adobe PDF/PostScript streams and git's binary patch format use Ascii85 instead of Base64. For URLs and email, Base64 is still the safer default since Base85's punctuation can break in those contexts.

Question 2

What is the difference between Ascii85 and Z85?

Accepted Answer

Both pack 4 bytes into 5 characters, but they use different alphabets. Adobe Ascii85 uses the 85 characters from `!` (33) to `u` (117), which includes characters like backslash and quotes that are awkward inside source strings. ZeroMQ's Z85 (RFC 32/Z85) was designed so the output is safe to paste directly into source code, JSON and shell, so it avoids backslash, backtick and quote. Z85's spec officially only covers data whose length is a multiple of 4 bytes; this tool pads shorter input the Ascii85 way so arbitrary text still round-trips.

Question 3

What do the `<~` and `~>` markers around Ascii85 output mean?

Accepted Answer

They are Adobe's start and end delimiters for an Ascii85 stream. PDF and PostScript wrap encoded data as `<~....~>` so a parser knows exactly where the encoded block begins and ends. They are optional: the raw five-character groups decode fine without them. This tool can add them on encode (the wrap checkbox) and always recognizes and strips them on decode, so you can paste a PDF stream fragment straight in. The decoder is lenient and also tolerates whitespace between the markers.

Question 4

What does the `z` shortcut do in Ascii85?

Accepted Answer

When a full four-byte group is all zeros (0x00000000), Ascii85 would normally produce five `!` characters. Instead the spec lets you write a single `z` to stand for that whole group, which shrinks long runs of zero bytes dramatically, common in sparse binary data. For example four zero bytes encode to just `z`. Note `z` is only valid for a complete zero group at a group boundary; a `z` appearing mid-group is an error, and this tool reports it rather than guessing.

Question 5

How does it handle Chinese characters and emoji?

Accepted Answer

Text is converted to UTF-8 bytes with the browser's TextEncoder before any Base85 math happens, and decoding runs TextDecoder('utf-8') on the recovered bytes. So `你好` becomes its 6 UTF-8 bytes, gets packed into Base85, and comes back as `你好` exactly. Emoji like `🚀` are 4-byte UTF-8 sequences and survive the same way. This avoids the classic bug where naive byte handling mangles anything above the ASCII range, and it means the tool is a real Unicode codec, not an ASCII-only one.

Base85 / Ascii85 Encoder & Decoder: Ascii85 and Z85, UTF-8 Safe

What this tool does

Tool details

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1. Input

2. Process

3. Copy / Download

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Base85 / Ascii85 Encoder & Decoder: Ascii85 and Z85, UTF-8 Safe

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Base85 / Ascii85 Encoder & Decoder fits into your work

Encoding jobs

Encoding checks

Good next steps

FAQ

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