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UUencode & UUdecode Tool
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Convert binary data to uuencoded text and vice versa online. Supports full format parsing, ideal for processing legacy emails and files.
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
UUencode is a legacy way to represent bytes with printable characters so data could pass through text-only channels. This page accepts text and encodes its UTF-8 bytes, or decodes uuencoded body text back into a UTF-8 text display. It does not accept a file, choose an output filename, or apply file permissions. A readable result is a text view; it does not prove that arbitrary binary data has been restored as a usable file.
Traditional UU data is arranged in lines. The first character on a body line represents the number of original bytes on that line. The remaining characters carry groups of three bytes encoded as four six-bit values. A zero-count line marks the end of the body and is commonly shown as a backtick. A conventional file block may also wrap the body in a begin mode filename header and an end trailer.
3 input bytes → 4 printable body characters
Each body line begins with a character-count marker; a zero-count line ends the data.
The page’s encoder emits the body and zero-count line, without a filename, mode header, or end trailer. The decoder accepts body text and can strip a header on the first line and an end line at the end. The format and the page’s exact behavior are different details: OpenBSD’s format manual describes the conventional framed file form.
Encoding changes how bytes are represented; anyone with the text can reverse it. It does not require a secret key and does not provide confidentiality, identity checks, or tamper protection. Use an encryption method designed for the security requirement when information must be protected.
Base64 is another binary-to-text encoding used in modern formats such as MIME. UUencode and Base64 are not interchangeable byte-for-byte: their alphabets and framing conventions differ. Identify the expected format before decoding a snippet.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Use the encoding mode and type or paste the text you want represented. The input is converted to UTF-8 bytes before encoding.
Copy the generated lines with their line breaks, leading count characters, and final zero-count marker. The page does not add file metadata or a trailing end line.
The encoder has a known compatibility edge case for some multibyte text. Independently decode its output with the receiving system or a trusted UU implementation and compare the result with the original before using it for migration or archival work.
Paste the body lines, or a complete block whose first line begins begin and whose final line is end. It does not search an entire email for an embedded block.
Do not wrap, merge, or edit lines. Remove email quote marks and surrounding commentary so they are not mistaken for UU data.
Compare the result to a known original where possible. If it shows replacement characters or unreadable text, the body may be damaged or the decoded bytes may represent binary data rather than UTF-8 text.
Use cases
See how the tool fits into real work and everyday tasks.
Paste a clearly bounded UU body from an old message or archive to see whether it contains readable UTF-8 text.
Compare a short input with its encoded body to see the count marker and printable groups, then decode it to understand the reversible transformation.
Review a short text sample in documentation or a test fixture. For real file recovery, use a file-capable UU decoder and compare the recovered bytes.
Q&A
Find concise answers to common questions and confusing cases.
No. The page can decode a body by itself. It also removes a header only when it is on the first line and removes end only when it is on the last line.
The result is a UU body with its zero-count terminator. It has no filename or mode field, and no final end line, so add framing only if the receiving workflow specifically requires it.
The body may have missing or altered characters, or it may decode to bytes that are not UTF-8 text. This page displays text rather than saving arbitrary bytes to a file.
No. It is reversible encoding, not encryption; it offers no secrecy.
Notes
Review scope, result limitations, and important precautions before use.
Verify encoded output independently: the current encoder is not reliable for every multibyte input. Do not use its output as the sole copy for migration, archival, or system exchange; verify with the receiving implementation and compare the decoded text.
Related
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