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Category Code Utilities

Operation Mode

Encode Decode

Standard / Specification

Uses <~ ~> delimiters. 'z' for nulls.

Compression ('z' for nulls) Split lines (76 chars) Include delimiters (<~ ~>)

Input Size: 0 B

Output Size: 0 B

Ratio: --

Input Data

Drop file to load binary data

Enter data to see the block conversion logic.

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About

Base85 is not a single standard; it is a family of binary-to-text encoding schemes used where bandwidth or storage efficiency is critical. While Base64 expands data by roughly 33.3%, Base85 limits this expansion to 25% by utilizing a larger ASCII alphabet. This makes it the standard choice for embedding bitmaps in PostScript/PDF files (Adobe Standard) and for compact messaging in ZeroMQ (Z85).

However, the ecosystem is fragmented. A string encoded in Adobe Ascii85 will produce garbage output if decoded using the Z85 standard due to different alphabet mappings and padding rules. This tool acts as a universal bridge, offering automatic standard detection, hex-level inspection for binary recovery, and strict compliance with RFC 1924 (IPv6), Adobe, and ZeroMQ specifications.

Formulas

Base85 operates on 32-bit integer blocks. The conversion process is a change of base from Base-256 (Bytes) to Base-85.

{

Input Block: B = [b₁, b₂, b₃, b₄]Integer: N = 4∑i=1 b_i × 256⁴⁻ⁱOutput: Char_k = ⌊ N85^k ⌋ mod 85

For Adobe Ascii85, the ASCII character is Char_k + 33. For Z85, Char_k is an index into a lookup table.

Reference Data

Standard / Spec	Alphabet Range	Special Features	Zero Compression	Padding Logic	Primary Usage
Adobe Ascii85	! thru u	Delimiters <~ ~>	YES (uses 'z')	Append nulls, output chars	PDF, PostScript
ZeroMQ (Z85)	0-9, a-z, A-Z, symbols	String-safe (no quotes)	NO	Strict (Error if length ≠ 4x)	MQ Messaging, CurveCP
IPv6 (RFC 1924)	0-9, A-Z, a-z, symbols	Math-oriented mapping	NO	None (Fixed 128-bit)	Compact IP Representation
BTOA	! thru u	Legacy Unix tool	YES (uses 'z')	Prepends length byte	Legacy Binary Transfer
Base64	A-Z, a-z, 0-9, +, /	Universal compatibility	NO	Uses "="	MIME, Web, Data URIs
Base91	ASCII 33-126	Variable length output	NO	Complex bitstream	High efficiency storage

Frequently Asked Questions

The most common cause is a Standard Mismatch. Adobe Ascii85 and ZeroMQ (Z85) use different alphabets. If you decode a Z85 string using the Adobe standard, the byte values will be completely wrong. Try switching the "Standard" dropdown.

In the Adobe specification, "z" is a compression shorthand. It represents a 32-bit block of zeros (0x00000000). Instead of outputting five exclamation marks ('!!!!!'), the system outputs a single "z", saving 4 bytes per block of empty space.

Yes. Paste the Base85 string into the input. Select "Decode". Once processed, check the "Hex Preview" tab. If you see file headers (like %PDF or ‰PNG), use the "Download Binary" button to save the result as a file.

Base85 is significantly more efficient for large binaries. Base64 increases size by 33%, whereas Base85 increases it by only 25%. For a 100MB file, Base85 saves approximately 8MB of transfer overhead compared to Base64.

Z85 is designed for code string literals and network packets where byte-for-byte exactness is required. Whitespace could be interpreted as formatting rather than data, so the standard strictly forbids it to prevent ambiguity.