A portable media player (PMP) is a consumer electronics device that is capable of storing and playing digital media such as audio, images, video, documents, etc. the data is typically stored on a hard drive, microdrive, or flash memory. In contrast, analog portable audio players play music from cassette tapes, or records. Often digital audio players are sold as MP3 players, even if they support other file formats. Other types of electronic devices like cellphones, internet tablets, and digital cameras are sometimes referred as PMPs because of their playback capabilities. This article however focuses on portable devices that have the main function of playing media.

MP3 players are portable CD players that can decode and play MP3 audio files stored on CDs. Such players are typically much less expensive than either the hard drive or flash based players. Also, the blank CD-R media is very inexpensive, typically costing less than US$0.15 per disk. In addition, these devices have the added bonus of being able to play standard red book audio CDs. A disadvantage is that due to the mechanical nature of these devices, they are even more fragile than the hard drive based players, and thus more susceptible to skipping or other misreads of the file during playback if mishandled. However, some of the more expensive, higher end units are also capable of reading and playing back files contained on larger capacity DVD disks as well, including the ability to playback and display video content, such as movies. In 2001 MP3 players functionality began to appear in mobile phones. The idea spread across the globe and by 2005 all major handset makers had released music phones. By 2006, more MP3 players were sold in mobile phones than all stand alone MP3 players put together.

An MP3 CD is a compact disc that contains digital audio in the MP3 file format. Discs are burned in the yellow book standard data format as opposed to the red book standard audio format. MP3 files are supported by many modern CD players, including DVD players. Because of audio data compression, an MP3 CD does not have to spin all of the time, potentially saving battery power. The song is buffered in random access memory, which also provides protection against skipping. A CD can typically hold only around 700 megabytes of data, thus a large library will require multiple disks to contain.

The name MP4 player is a marketing term for portable media players that comply with certain standards and formats. The name itself is a misnomer, since most MP4 players are incompatible with the MPEG-4 or the .mp4 container format. Instead, the term symbolizes their status as successors of MP3 players. In this sense, in some markets like Brazil, any new function added to a given media player is followed by an increase in the number, despite there being no corresponding MPEG-5 standard. These players can play video in a multitude of video formats without the need to convert them or downsize them prior to playing them. Some MP4 Players possess USB ports in order for the users to connect it to a PC. Some have memory cards to expand the memory of the player instead of storing files in the built in memory.