What is yEnc ?

yEnc Decoder -How to view files
yEnc Encoder -How to encode files
History of yEnc -Why encode?

Outlook Express yEnc Decoder

If you're new to newsgroups no doubt you're new to yEnc downloads. It's become commonplace to see yEnc encoding on most message headers after you download a file from a popular newsgroup, such as Usenet. Many Outlook Express users who access newsgroups are often confused when their picture, mp3 or video file finally arrives and is not viewable because it was encoded by yEnc. The good news is, you came to the right place for help. The better news is, you're going to quickly learn how to decode yEnc files!

A newsreader yEnc file

What is a yEnc encoded file?

yEnc is a method of encoding binary message attachments in a way that will survive Usenet's Network News Transfer Protocol (NNTP).

Here's old encoding methods. They're nice and safe, and BIG, and SLOW:

Here's yEnc. It's sleek, and SMALL and FAST:

All binary files on Usenet must be encoded.
Why not pick the smaller, faster one?

Why do we need to encode binary attachments?

Unlike the web protocol (HTTP), which supports transferring raw data, NNTP does not include such a feature. With NNTP, there is no way to say "Everything that follows is raw data". With NNTP, the carriage return and line feed characters always signify a new line and are not considered part of the data, and null characters are simply not allowed. NNTP requires that all messages use only printable US ASCII characters.

NNTP Messages have the following requirements:
1) Each line ends with a carriage return and line feed
2) Only printable US ASCII characters can be used

Besides the fact that NNTP was designed with only text messages in mind, a side effect of supporting only printable characters was that it allowed older operating systems that have a limited character set to support NNTP.

Eventually, people wanted to attach binary files to their text messages on Usenet. Therefore, encoding mechanisms were developed to send raw binary files over NNTP. The files were encoded in a format that would survive being sent in the required format for NNTP.

What yEnc is not

yEnc is not a type of compression. yEnc is not a file format. yEnc is simply an intermediary transport mechanism. You can think of yEnc like a envelope. You just need a program that can open the envelope. The files inside of the envelope are just normal files.

Why is yEnc so popular?

yEnc is over 30% smaller than the traditional format. Because it's smaller, yEnc encoded posts are faster for you to download, and faster for the poster to upload. It's a win/win encoding format.

Why doesn't my newsreader support yEnc?

I really don't know why some of the standard free newsreaders like Outlook Express, Windows Mail, Thunderbird, and Opera don't support yEnc. However, you can use yProxy to automatically decode your yEnc encoded news messages. yProxy is a yEnc decoder that works with any standard news reader.

Why is there such a debate about yEnc in some newsgroups?

Some people feel that MIME could have easily been modified to include an 8-bit encoding method. However, yEnc has been popular for at least 7 years, and there is still no sign of a 8-bit MIME encoding format. Users don't like to wait. yEnc is here, so people are using yEnc. Some people like to gripe about what should be.

yEnc Resources

You can read more about yEnc Decoders here.