M3U

Key takeaways

M3U belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect M3U to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of M3U from memory before moving on to harder problems.

Reference excerpt

M3U (MP3 URL) is a computer file format for a multimedia playlist. One common use of the M3U file format is creating a single-entry playlist file pointing to a stream on the Internet. The created file provides easy access to that stream and is often used in downloads from a website, for emailing, and for listening to Internet radio. Although originally designed for audio files, such as MP3, it is commonly used to point media players to audio and video sources, including online sources. M3U was originally developed by Fraunhofer for use with their WinPlay3 software, but numerous media players and software applications now support the format. Careless handling of M3U playlists has been the cause of vulnerabilities in many music players such as VLC media player, iTunes, Winamp, and many others.

File format There is no formal specification for the M3U format; it is a de facto standard. An M3U file is a plain text file that specifies the locations of one or more media files. The file is saved with the m3u filename extension if the text is encoded in the local system's default non-Unicode encoding (e.g., a Windows codepage), or with the m3u8 extension if the text is UTF-8 encoded. The mp3url extension was originally supported by Winplay3, but fell out of use. Each entry carries one specification. The specification can be any one of the following:

an absolute local pathname; e.g., C:\My Music\Heavysets.mp3 a local pathname relative to the M3U file location; e.g. Heavysets.mp3 a URL Each entry ends with a line break which separates it from the following one. Furthermore, some devices only accept line breaks represented as CR LF, but do not recognize a single LF.

Extended M3U The M3U file can also include comments, prefaced by the # character. In extended M3U, # also introduces extended M3U directives which are terminated by a colon : if they support parameters.

M3U8 The use of UTF-8 encoding is mandatory in M3U playlists with the M3U8 file extension. The system codepage is usually assumed for .m3u but this is often UTF-8 as well nowadays so the distinction has mostly been lost in practice.

HLS Apple used the extended M3U format, UTF-8 encoded, as a base for their HTTP Live Streaming (HLS) which was documented in an Independent Submission Stream RFC in 2017 as RFC 8216. Therein, a master playlist references segment playlists which usually contain URLs for short parts of the media stream. Some tags only apply to the former type and some only to the latter type of playlist, but they all begin with #EXT-X-.

IPTV With television broadcasting via the internet protocol (IPTV), M3U playlists are frequently used to store the (start) URLs of the streams, so each entry represents a channel. As usual for continuous streams, the length info directly after #EXTINF: is set to -1. Unlike HLS, other structured information is not provided in separate info lines but with a key–value syntax before the mandatory comma following the length.

Internet media types The only Internet media type registered for M3U and M3U8 is application/vnd.apple.mpegurl, registered in 2009 and only referring to the playlist format as used in HLS applications. The current proposal for the HLS playlist format acknowledges two media types which it treats as equivalent: application/vnd.apple.mpegurl and audio/mpegurl. Likewise, these are the two types recommended for HLS use by Microsoft. For non-HLS applications, no media types were standardized or registered with the IANA, but a number of media types are nonetheless associated with the historical and ongoing use of the M3U and M3U8 formats for general playlists:

application/mpegurl application/x-mpegurl audio/mpegurl audio/x-mpegurl These types, plus application/vnd.apple.mpegurl and application/vnd.apple.mpegurl.audio, are supported for HLS applications by (for example) Microsoft's Windows 10 and Internet Explorer 9, and LG's WebOS.

Example The following is an example of an M3U playlist file for the Alice in Chains album Jar of Flies that was created by Mp3tag with the following custom option settings:

playlist extended info format = "%artist% - %title%" playlist filename format = "%artist%_%album%_00_Playlist.m3u" tag to filename conversion format = "%artist%_%album%_$num(%track%,2)_%title%" #EXTM3U #EXTINF:419,Alice in Chains - Rotten Apple Alice in Chains_Jar of Flies_01_Rotten Apple.mp3 #EXTINF:260,Alice in Chains - Nutshell Alice in Chains_Jar of Flies_02_Nutshell.mp3 #EXTINF:255,Alice in Chains - I Stay Away Alice in Chains_Jar of Flies_03_I Stay Away.mp3 #EXTINF:256,Alice in Chains - No Excuses Alice in Chains_Jar of Flies_04_No Excuses.mp3 #EXTINF:157,Alice in Chains - Whale And Wasp Alice in Chains_Jar of Flies_05_Whale And Wasp.mp3 #EXTINF:263,Alice in Chains - Don't Follow Alice in Chains_Jar of Flies_06_Don't Follow.mp3 #EXTINF:245,Alice in Chains - Swing On This Alice in Chains_Jar of Flies_07_Swing On This.mp3

Software

Tag editors

The following tag editor software allows users to edit the ID3 tags in MP3 files, and has support for creating M3U files.

Linux Kid3, Puddletag. Windows Mp3tag, Puddletag. macOS Mp3tag.

Media players

The following media player software supports playing M3U files.

Multi-platform

Android Astro Player, Kodi, N7Player, Musicolet macOS Music, QuickTime Player, IINA Nintendo New Nintendo 3DS (including XL and 2DS XL variants) with Internet Browser app Nintendo Switch with the YouTube (site-specific) app Wii U with the Internet Browser or YouTube app Windows foobar2000, JRiver Media Center, JuK, MediaMonkey, PotPlayer, Winamp, Windows Media Player, XMPlay

See also List of tag editors Other playlist file formats PLS - SHOUTcast

References

External links "Unofficial M3U and PLS file specification". Forum. Tech Support Greatest Hits. WinAmp. 2008 [2001]. Gonze, Lucas (2003). "Survey of playlist formats". Draft. May, W. (2017). Pantos, R. (ed.). "HTTP Live Streaming specification". Draft. IETF. Includes M3U and M3U8 Creating Playlists to Work with the Streaming Music Manager

Worked examples

Example 1 — a first encounter with M3U

Start with the simplest possible case. Write down what M3U claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to M3U before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about M3U ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of M3U

In research: M3U appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses M3U in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: M3U is common in secondary-school and first-year university syllabi. It links to neighbouring topics Digital audio, Filename extensions, Playlist file formats, so understanding it makes those chapters shorter.
In everyday life: Look for M3U outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study M3U in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what M3U means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain M3U out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is M3U in simple terms?

M3U (MP3 URL) is a computer file format for a multimedia playlist. One common use of the M3U file format is creating a single-entry playlist file pointing to a stream on the Internet.

Why does M3U matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study M3U?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on M3U.