Inside M3U: How the Playlist Format Works
An M3U file is a plain-text playlist file used to tell a media player where audio or video files are located. The name comes from MP3 URL, although M3U playlists can reference many types of media, not just MP3s.
What an M3U File Contains
An M3U file doesn't usually contain the media itself. Instead, it contains paths or URLs pointing to media files.
Example:
song1.mp3
song2.mp3
C:\Music\song3.mp3
https://example.com/stream.mp3
When opened in a compatible media player, the player loads and plays the listed files in order.
Extended M3U (M3U8)
Many playlists use an extended format that begins with:
#EXTM3U
Additional metadata can be included:
#EXTM3U
#EXTINF:245,Artist Name - Song Title
song1.mp3
#EXTINF:180,Another Artist - Another Song
song2.mp3
Here:
#EXTM3Uindicates an extended playlist.#EXTINFprovides media information.- The number is the duration in seconds.
- The text is the display title.
M3U8
M3U8 is simply an M3U file encoded in UTF-8, allowing support for international characters. It is also widely used in HTTP Live Streaming (HLS), a streaming technology developed by Apple.
Example HLS playlist:
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:10
#EXTINF:10,
segment1.ts
#EXTINF:10,
segment2.ts
#EXT-X-ENDLIST
Common Uses
- Music playlists
- Video playlists
- Internet radio streams
- IPTV channel lists
- HLS video streaming
Opening an M3U File
Many media players support M3U playlists, including:
- VLC media player
- Winamp
- Kodi
- Windows Media Player
IPTV Example
An IPTV playlist often looks like:
#EXTM3U
#EXTINF:-1 tvg-id="news1" tvg-name="News Channel",News Channel
http://stream.example.com/live/news.m3u8
#EXTINF:-1 tvg-id="sports1" tvg-name="Sports Channel",Sports Channel
http://stream.example.com/live/sports.m3u8
The playlist contains channel information and stream URLs that IPTV applications can load.
The Extended M3U Format: Core Tags
An "Extended M3U" file offers more functionality through specific directives. All extended files must start with #EXTM3U on the first line.
Here is a list of the key directives for the Extended M3U format:
| Directive | Description | Example |
|---|---|---|
#EXTM3U |
File header indicating an Extended M3U file; must be the first line. | #EXTM3U |
#EXTENC: |
Specifies the text encoding of the file, usually placed as the second line. | #EXTENC:UTF-8 |
#EXTINF: |
Specifies track information, most commonly the duration (in seconds) and a display title. For live streams, the duration is often set to -1. |
#EXTINF:123,Artist - Song Title |
#PLAYLIST: |
Defines the title of the entire playlist. | #PLAYLIST:My Favorite Podcasts |
#EXTGRP: |
Marks the beginning of a named grouping for tracks or channels. | #EXTGRP:Rock Classics |
#EXTALB: |
Provides album information for the following track. | #EXTALB:Dark Side of the Moon |
#EXTART: |
Specifies the album's artist. | #EXTART:Pink Floyd |
#EXTGENRE: |
Indicates the genre of the album or track. | #EXTGENRE:Progressive Rock |
#EXTM3A |
A single-file playlist used for album tracks or chapters. | #EXTM3A |
#EXTBYT: |
Specifies the file size in bytes. | #EXTBYT:8482812 |
#EXTBIN: |
Indicates that binary data follows. | #EXTBIN: |
#EXTIMG: |
Provides a URL for a logo, cover art, or other images. | #EXTIMG:https://example.com/logo.png |
Specialized Tags for IPTV Playlists
In IPTV contexts, additional attributes are often used inside the #EXTINF line to provide rich metadata for Electronic Program Guides (EPGs) and channel organization.
| Tag / Attribute | Description | Example |
|---|---|---|
tvg-id |
A unique identifier for the channel, used to match it with EPG data. | tvg-id="cnn.us" |
tvg-name |
The channel name as it appears in the EPG file. | tvg-name="CNN International" |
tvg-logo |
A URL pointing to the channel's logo image (usually PNG format). | tvg-logo="https://example.com/logos/cnn.png" |
group-title |
Defines the group or category for the channel. | group-title="News" |
tvg-url |
A URL to the EPG (Electronic Program Guide) data file, often in XMLTV or JTV format. | tvg-url="https://example.com/epg.xml.gz" |
channel-number |
Specifies a custom channel number to be displayed to the user. | channel-number="105" |
refresh |
Defines the playlist refresh period in seconds. | refresh="3600" |
Example of an IPTV #EXTINF line:
#EXTINF:-1 tvg-id="bbcnews.uk" tvg-name="BBC News" tvg-logo="https://example.com/bbc.png" group-title="News",BBC News
Advanced HLS Tags (#EXT-X-)
For HTTP Live Streaming, the M3U8 format uses a specific set of tags prefixed with #EXT-X-. These tags are defined in the IETF RFC 8216.
| Tag | Description | Example |
|---|---|---|
#EXT-X-VERSION |
Indicates the compatibility version of the playlist and its server. | #EXT-X-VERSION:3 |
#EXT-X-TARGETDURATION |
Specifies the maximum duration (in seconds) for each media segment. | #EXT-X-TARGETDURATION:10 |
#EXT-X-MEDIA-SEQUENCE |
Indicates the sequence number of the first media segment in the playlist. | #EXT-X-MEDIA-SEQUENCE:0 |
#EXT-X-KEY |
Specifies how to decrypt media segments that are encrypted. | #EXT-X-KEY:METHOD=AES-128,URI="https.../key.bin" |
#EXT-X-PROGRAM-DATE-TIME |
Associates the first sample of a media segment with an absolute date and/or time. | #EXT-X-PROGRAM-DATE-TIME:2024-01-01T00:00:00Z |
#EXT-X-DISCONTINUITY |
Indicates a discontinuity in the stream, such as a change in encoding parameters or ad insertion. | #EXT-X-DISCONTINUITY |
#EXT-X-ENDLIST |
Indicates that no more media segments will be added to the playlist (used for Video on Demand, VOD). | #EXT-X-ENDLIST |
#EXT-X-STREAM-INF |
In a master playlist, it specifies a variant stream (e.g., different bitrates or resolutions). | #EXT-X-STREAM-INF:BANDWIDTH=1500000,RESOLUTION=1280x720 |
#EXT-X-MEDIA |
Relates media playlists that contain alternative renditions of the same content (e.g., different audio languages). | #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",LANGUAGE="en",URI="..." |
#EXT-X-I-FRAME-STREAM-INF |
Defines an I-frame-only variant stream for seeking or thumbnail generation. | #EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=50000,URI="iframes.m3u8" |
#EXT-X-BITRATE |
Provides the bitrate of the media segment or variant stream. | #EXT-X-BITRATE:128000 |
#EXT-X-DATERANGE |
Associates a date range (e.g., for ad breaks or program segments) with the playlist. | #EXT-X-DATERANGE:ID="ad1",START-DATE="2025-01-01T00:00:00Z" |
Player-Specific Tags
Some tags are specific to certain media players. The most common ones are for VLC, which uses the #EXTVLCOPT directive to pass options directly to the player.
| Tag | Description | Example |
|---|---|---|
#EXTVLCOPT: |
Passes a configuration option to the VLC media player (e.g., for network referrers or HTTP headers). | #EXTVLCOPT:http-referrer=https://example.com/ |
Advantages
- Simple text format
- Easy to edit with any text editor
- Supported by many media players
- Can reference local files or online streams
Limitations
- Does not store the actual media
- Broken paths or URLs make entries unusable
- Limited metadata compared with some modern media library formats
In short, an M3U file is a lightweight playlist format that acts as a list of media locations, making it easy to organize and play collections of audio, video, or streaming content.
UD X-File Editorial Team
Verified updates, firmware releases and technical news.
Verified updates, firmware releases and technical news.
