Base91 Decoder

Summary

Base91 is a binary-to-text encoding scheme created by Joachim Henke that encodes binary data using 91 printable ASCII characters. Compared to Base64 (33% overhead) and Base85 (25% overhead), Base91 achieves roughly 23% overhead, making it one of the most space-efficient text-safe encodings available. This tool decodes any Base91-encoded string back to its original plain text entirely in your browser — nothing is sent to a server.

How it works

1. Paste your Base91-encoded string into the input field.
2. Click the Decode button (or decoded output updates as you type).
3. The tool processes pairs of characters using the 91-character alphabet.
4. Each pair encodes 13 bits, yielding up to 1.625 bytes per character on average.
5. The decoded text appears in the output panel immediately.
6. Use the Copy button to copy the result to your clipboard.

Use cases

• Decode Base91 payloads found in source code or config files.
• Reverse Base91-encoded strings from scripts or shell one-liners.
• Verify that a Base91 encoded value matches expected plaintext.
• Inspect Base91 data during security research or reverse engineering.
• Decode Base91 snippets from network captures or log files.
• Test Base91 round-trips when building encoding utilities.
• Recover text from Base91-encoded clipboard content.
• Compare Base91 output size against Base64 or Base85 alternatives.

Frequently Asked Questions