Quoted-Printable

Quoted-Printable is a MIME content transfer encoding for mostly-ASCII text: only non-printable characters are escaped as =HH, keeping most of the text readable.

Purpose

When text is mostly ASCII with only a few non-ASCII characters, it expands far less than Base64 and stays human-readable.

Mechanism

Printable ASCII (33-126, except =) passes through unchanged; every other byte becomes = followed by two uppercase hexadecimal digits. Line endings use = soft line breaks (encoded lines stay within 76 characters), and spaces or tabs at the end of a line must also be escaped.

Use cases

Email bodies in Chinese and European languages
vCard contact field encoding
MIME header parameter values
SMTP UTF-8 fallback

Examples

Input
```
café
```
Output
```
caf=C3=A9
```
é (U+00E9) encodes to UTF-8 bytes C3 A9, escaped as =C3=A9

Common errors

Unescaped trailing spaces being lost during decoding: Strictly follow RFC 2045: escape trailing spaces as =20 and tabs as =09

Related terms

MIME (Multipurpose Internet Mail Extensions) encoding defines the mechanisms for transporting non-ASCII text and binary attachments in email, including the Base64 and Quoted-Printable content transfer encodings.

Base64 maps arbitrary binary data onto 64 printable ASCII characters (A-Z, a-z, 0-9, +, /) so that binary data can travel over text-only channels.

A character set (charset) is the mapping table from characters to code points; together with an encoding form (such as UTF-8) it determines how text becomes a byte stream.

Related tools

Quoted-Printable Encoder

Encode text to Quoted-Printable format (RFC 2045). Free, private, and 100% client-side.

Quoted-Printable Decoder

Decode Quoted-Printable text back to original content. Free, private, and 100% client-side.

References