=?UTF-8?B?Q2Fmw6kgbWVldGluZyBub3Rlcw==?=
About MIME Encoded-Word Encoder / Decoder (RFC 2047)
MIME encoded-words let email headers carry non-ASCII text. Headers like Subject and the display name in From are restricted to 7-bit ASCII, so any accented letter, emoji, or non-Latin script must be wrapped in the RFC 2047 form =?charset?encoding?text?= — for example =?UTF-8?B?Q2Fmw6k=?=. This tool turns plain text into those encoded-words and decodes them back to readable text.
It supports both transfer encodings defined by RFC 2047: B (Base64) and Q (a quoted-printable variant where bytes become =XX and spaces become _). Long input is split into multiple encoded-words that each stay within the 75-character limit, and decoding stitches adjacent words back together exactly as a mail client would.
Everything runs locally in your browser. Whether you are debugging a garbled Subject line or constructing a header by hand, nothing you paste is ever uploaded.
Features
- Encode text to RFC 2047 encoded-words and decode them back
- Both B (Base64) and Q (quoted-printable) transfer encodings
- Full UTF-8 support — accents, non-Latin scripts, and emoji
- Decodes mixed input, preserving literal text around encoded-words
How to use
- Paste plain text to encode, or a =?…?= encoded-word to decode.
- Choose Encode B or Encode Q for the transfer encoding, or Decode for the reverse.
- Copy the result from the output pane — or clear and start again.
Frequently asked questions
What is a MIME encoded-word?
It is the RFC 2047 syntax =?charset?encoding?text?= used to put non-ASCII characters into email headers such as Subject and From. The charset is usually UTF-8, and the encoding is B (Base64) or Q (quoted-printable).
What is the difference between B and Q encoding?
B uses standard Base64 over the raw bytes. Q is a quoted-printable variant: printable ASCII passes through, a space becomes _, and other bytes become =XX in uppercase hex. Q is more readable for mostly-ASCII text; B is more compact for heavily non-ASCII text.
Why is my Subject line showing =?UTF-8?B?…?= literally?
A mail client that fails to decode an encoded-word displays it raw. Paste it into the Decode action here to see the intended text, which usually confirms the header itself is well-formed and the client is at fault.
Does my data get sent anywhere?
No. All encoding and decoding happens locally in your browser using the built-in TextEncoder, TextDecoder, and btoa/atob APIs. Your input never leaves your device.
Related tools
Everything runs locally in your browser — your input is never uploaded.