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UUencode Encoder

Encode text to UUencode or decode it back, the classic Unix format for sending binary files as text. Output includes the begin header and end footer lines.

UUencode

Text to encode, or UUencode to decode.

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How UUencode works

UUencode reads 45 bytes per line, splits them into 3-byte groups, and maps each group to 4 printable characters starting at ASCII 32. The line starts with a length character, and the whole payload is framed by begin 644 output.bin and end lines, a format Unix mail programs understood in the 1980s.

Where UUencode survives today

Modern email uses Base64, but UUencode still appears in retro computing, old Usenet archives, legacy scripts and certification exams. Knowing how to decode it is useful when you inherit very old tooling or data.

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UUencode Encoder FAQs

What do the begin and end lines mean?
begin 644 output.bin declares the file permissions and name, and a line with end marks the payload end. This tool emits both so the output matches the classic format decoders expect.
Why does each line start with M?
The first character encodes the line length: M means 45 bytes, the standard full line. Shorter final lines start with a different character, and a lone backtick marks zero length.
How is this different from Base64?
Both encode binary as text, but UUencode uses a different alphabet, includes framing headers, and expands data by about 35 percent versus 33 for Base64. They are not interchangeable.
Does it support Unicode text?
Yes. Input is encoded as UTF-8 bytes first, so any Unicode text round-trips correctly through encode and decode.
Is my text uploaded?
No. Encoding and decoding run entirely in your browser, so your data never leaves your device.
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