... Most of the following formats are technically known as "lossy codecs", which basically means that they are smaller files than the original because they have removed some data. They should still sound the same to you or I.

MP3 is the most famous format, but it's a bit long in the tooth these days, because other formats either sound better, take up less space, or both.

Facts about MP3

• Popular - when it comes to technology, going with the flow is sound advice.
  
• Not open source - in theory you need to obtain a license from Fraunhofer IIS to create a product that encodes or decodes MP3.
  
• Old - it has been around since 1987, leaving plenty of time for better technologies to be created. Read the official history
  
• Space hungry - a normal 10 second .wav (CD quailty) stereo audio file takes up 1.72Mb of space on the hard disc. The same file compressed in Mp3 format at the highest setting occupies only 313Kb, with minimal loss in sound quality. This is why it was so hugely popular. However, other formats can take up less space with better quality
  
• No DRM - no digital rights managment, which means it is virtually impossible to sell MP3s online
  

At the moment this looks like it will win in the long-term, thanks to Windows Media Player. We predict Apple iPod users and their AAC will eventually be the same as Apple Mac users are today - loyal but few.

Facts about WMA

• Not open source - in fact the knowledge that it is Microsoft's product might put some people off.
  
• Popular - if you want to buy tracks online, most offerings are in this format, because it supports digital rights management. Also, it goes hand in hand with Microsoft's Media Player, something most of us already have for free
  
• Space friendly - takes up less space than MP3s, while reproducing the same quality
  
• DRM - digital rights management

The follow-up codec to MPeG1 Layer3 (MP3). AAC was developed (just like MP3) by the "Fraunhofer Institut für integrierte Schaltungen". AAC (advanced audio compression/decompression) sounds better than MP3 - 96kbps compression are sufficient for good sound quality. Moreover AAC is secure - that is why Liquid Audio & Apple use it. However high licensing costs have kept this audio codec from being universal.

Facts about AAC

• Not open source or free
• Semi-Popular - the success of the format revolves around Apple's ability to keep iPods popular.
• Space friendly - AAC compressed audio at 96 kbps generally exceeded the quality of MP3 compressed audio at 128 kbps, and it takes up less space. More...
• DRM - enables us to buy tracks from iTunes.com

Ogg Vorbis is a completely open, patent-free, professional audio encoding and streaming technology with all the benefits of open source.

Facts about OGG

• Space friendly - for a given file size, Vorbis sounds better than MP3. You can have better quality for the same file size, or equal quality with a smaller file size
• Free - no royalties
• Semi-Popular - widespread player support.

For more information on OGG, visit:

• Ogg Vorbis - the official homepage

A lossless format, which means smaller file sizes but absolutely no loss of data.

• Quality - perfect sound – absolutely no quality loss, meaning it sounds perfect and decompresses perfect (it's lossless!)
• Semi-Popular - Supported by many popular players and rippers, incl. Media Center & WinAmp
• Free
• Tagging support – Monkey’s Audio uses its own extremely flexible APE Tags so you can easily manage and catalogue your Monkey’s Audio collection.

For more information on Monkey's Audio, visit:

• Monkey's Audio - the official homepage