Skip to main content

quoted-printable-encoder

Quoted-printable (QP) is a MIME encoding (RFC 2045) that represents 8-bit data using only printable ASCII — necessary in email systems where some intermediaries still cannot reliably handle 8-bit content — by escaping non-printable and special bytes as =NN (where NN is the byte's hex value) and breaking long lines. The ZTools Quoted-Printable Encoder handles both encoding and decoding, supports the soft-line-break rules (lines ≤ 76 chars with = continuation), preserves UTF-8 multi-byte characters correctly, and is the right tool for inspecting raw email source or producing safe email-body content.

Use cases​

Reading raw email source​

Email clients show "Content-Transfer-Encoding: quoted-printable" with =E2=82=AC scattered through the body. Decode to read the original Unicode message.

Composing email programmatically​

A custom mail-sending script must produce QP for non-ASCII content. Encode message body before assembling the MIME message.

Debugging mojibake in email​

Garbled accented characters in delivered email. Trace through QP encoding to find the wrong-charset step.

Forensic email analysis​

Investigators read raw .eml files. QP decoding makes the content human-readable.

How it works​

  1. Pick mode — Encode (raw text → QP) or decode (QP → raw text).
  2. Paste content — Raw bytes (with declared charset) for encode; QP-formatted text for decode.
  3. Apply rules — Encode: bytes 33–60 + 62–126 pass through; others become =NN. Lines wrap at 76 chars with soft = line breaks. Decode: reverse, joining soft-broken lines.
  4. Inspect — Side-by-side original / encoded view; soft line breaks marked.
  5. Copy — Result to clipboard. Round-trip via the inverse mode for verification.

Examples​

Input: Hello, world! → encode

Output: Hello, world! (no special chars; passes through)

Input: café → encode (UTF-8)

Output: caf=C3=A9

Input: caf=C3=A9 → decode

Output: café

Frequently asked questions​

How is QP different from base64?

Base64 is a safer encoding for arbitrary binary, but inflates size by 33% and is less human-readable. QP is more efficient for mostly-ASCII text with occasional non-ASCII (only inflates the special bytes), and lets readers see most of the content directly.

What is a "soft line break"?

A line ending with =\\r\\n (in CRLF) or =\\n (LF). The decoder removes these, producing one logical long line. Used to satisfy the 76-character line-length rule without breaking content.

Should I encode "=" as "=3D"?

Yes — = itself is special and must be encoded as =3D always.

What about whitespace?

Spaces and tabs at end-of-line must be encoded (=20 / =09) because mail relays sometimes strip trailing whitespace.

Does it preserve UTF-8?

Yes — multi-byte UTF-8 sequences encode byte-by-byte (e.g. é = 0xC3 0xA9 → =C3=A9).

Why does my decoded email show "=" at end of lines?

Those are unencoded soft line breaks that the decoder did not recognise — usually due to wrong line endings (Mac CR vs Unix LF). Normalise line endings first.

Tips​

  • For programmatic email, use your language's MIME library rather than hand-encoding QP.
  • When debugging email mojibake, decode QP first, THEN check charset — the order of operations matters.
  • Soft line breaks are the most error-prone part of QP — pay attention to CRLF vs LF normalisation.
  • Round-trip via decode after encoding to verify nothing was lost.
  • For arbitrary binary, prefer base64 — QP is optimised for mostly-text content only.

Try it now​

The full quoted-printable-encoder runs in your browser at https://ztools.zaions.com/quoted-printable-encoder — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-05 · Author: Ahsan Mahmood · Edit this page on GitHub