basE91 Encoder and Decoder
encoding
Encode or decode basE91, a compact printable alphabet. Runs in your browser.
Encode or decode MIME quoted-printable text. Runs in your browser.
Runs in your browser — your input is processed on this device and never uploaded.
Enter text or upload a file to encode. To decode, enter the encoded text.
Results appear here.
Quoted-printable is a MIME content-transfer encoding for data that is mostly printable US-ASCII. Bytes that need escaping are written as an equals sign plus two hexadecimal digits. Long lines can fold with a soft line break, which is an equals sign at the end of the line.
SMTP and a lot of older mail paths were 7-bit. A message that is almost English, with a few accented characters or a copyright sign, does not need Base64's 33 percent overhead. Quoted-printable leaves the readable parts readable, so a raw message source still looks like the email.
That is also why it is a poor fit for binary. A JPEG encoded this way is larger and no longer skimmable.
Base64 Encoder and Decoder is the usual choice for attachments and anything that is not mostly text. HTML Entity Encoder and Decoder is for markup, not for MIME transport. URL Encoder and Decoder percent-encodes for URLs, which looks similar and is a different set of rules.
Quoted-printable does not encrypt or compress. Keep MIME headers and the declared character set with the message; this tool converts the body bytes only.
A trailing equals sign is a soft break, not data. Strict mode treats a broken hex escape as an error. Turning strict off is for cleaning up mail that already went through a careless gateway, not for inventing a dialect.
If you are looking at a full .eml file, strip or ignore the headers first. Feeding Content-Type lines through the decoder will not decode the body they describe.
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