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Base85 / Ascii85 Encoder & Decoder

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ガイド

Base85 / Ascii85 Encoder & Decoder

Encode text to Base85 or decode Base85-encoded data back to its original form. Base85 encoding converts 4 bytes of binary data into 5 printable ASCII characters, offering better space efficiency than Base64 (25% overhead vs 33%). This tool supports three major Base85 variants used across different applications.

使い方

Select your mode (Encode or Decode), choose a Base85 variant, paste your input text or encoded data, and click 変換する. The tool processes everything in your browser and displays the result along with input/output size comparison.

特徴

双方向 – Encode text to Base85 or decode Base85 back to original text
Three Variants – Ascii85 (Adobe/btoa with <~ ~> delimiters), RFC 1924 (Python/git), and Z85 (ZeroMQ)
Ascii85 Special Handling – Supports the ‘z’ shortcut for all-zero groups and automatic delimiter wrapping
サイズ比較 – Shows input vs output byte sizes with overhead percentage
Whitespace Tolerant – Decoder ignores whitespace in Ascii85 input for flexible pasting
Error Detection – Clear messages for invalid characters or malformed encoded data
クライアントサイドのみ – すべてのエンコードおよびデコードはブラウザ内で行われます

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 よくある質問

What is the difference between Base85 and Base64?

Both are binary-to-text encoding schemes, but they use different radixes. Base64 encodes 3 bytes into 4 characters (33% overhead), while Base85 encodes 4 bytes into 5 characters (25% overhead). Base85 is more space-efficient but uses a wider range of printable ASCII characters. Base64 is more widely supported across protocols and systems, while Base85 is commonly used in PostScript, PDF files, git binary patches, and ZeroMQ messaging.
What are the differences between Ascii85, RFC 1924, and Z85?

All three encode 4 bytes into 5 characters using base-85 arithmetic, but they differ in their character sets and conventions. Ascii85 (Adobe) uses characters ! through u (ASCII 33-117), wraps output in delimiters, and has a special 'z' shortcut for all-zero groups. RFC 1924 uses 0-9, A-Z, a-z, and selected symbols — this variant is used by Python and git. Z85 (ZeroMQ) uses its own character set optimized for embedding in source code and XML without escaping issues.
When should I use Base85 encoding?

Use Base85 when you need to embed binary data in text format and space efficiency matters more than universal compatibility. Common use cases include PostScript and PDF document streams (Ascii85), git binary diff patches (RFC 1924), ZeroMQ message framing (Z85), and any application where the 8% space savings over Base64 is significant for large payloads. For general web APIs and email attachments, Base64 remains the safer choice due to wider support.