Key HLS Tags: A Practical Reference for .m3u8 Manifests

HLS is defined by its tags. Each #EXT-X-* line in an .m3u8 carries one piece of instruction to the player, and knowing exactly what each one does turns a wall of text into a readable spec. This is a reference-style walk through the tags you will actually encounter, grouped by where they appear. If you want to see them parsed against a live stream, drop a manifest into the manifest inspector on the player page. For the bigger-picture structure, start with HLS Manifest Internals.

Basic / both playlists

EXT-X-VERSION

#EXT-X-VERSION:7

Declares the protocol version, which determines the legal feature set. Rough guide: version 3 for floating-point EXTINF durations, version 4 for EXT-X-BYTERANGE and I-frame playlists, version 5 for SAMPLE-AES, version 6 for EXT-X-MAP in media playlists, and version 7 for fMP4 segments. A player that does not support the declared version should refuse the playlist.

Master (multivariant) playlist tags

EXT-X-STREAM-INF

#EXT-X-STREAM-INF:BANDWIDTH=2600000,AVERAGE-BANDWIDTH=2350000,RESOLUTION=1280x720,FRAME-RATE=29.970,CODECS="avc1.64001f,mp4a.40.2",AUDIO="aud-en"
v720/index.m3u8

The most important tag in the master playlist. It declares one variant; the URI on the next line is its media playlist. Key attributes:

• BANDWIDTH (required) — peak bits per second of this variant including audio. This is the number ABR logic must keep below the estimated throughput.
• AVERAGE-BANDWIDTH — typical bits per second; smoother for steady-state decisions.
• CODECS — RFC 6381 codec strings (e.g. avc1.64001f for H.264 High@3.1, mp4a.40.2 for AAC-LC). Lets the player skip variants it cannot decode.
• RESOLUTION — pixel dimensions, used for display and for not upswitching past the viewport.
• FRAME-RATE — useful when a ladder mixes 30 and 60 fps rungs.
• AUDIO / SUBTITLES / CLOSED-CAPTIONS — group IDs binding this variant to EXT-X-MEDIA renditions.

EXT-X-MEDIA

#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aud-en",NAME="English",LANGUAGE="en",DEFAULT=YES,AUTOSELECT=YES,URI="audio/en/index.m3u8"
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="English",LANGUAGE="en",FORCED=NO,AUTOSELECT=YES,URI="subs/en/index.m3u8"

Declares an alternate rendition — typically a separate audio language or a subtitle track — that variants reference by GROUP-ID. DEFAULT=YES marks the track selected on startup; AUTOSELECT=YES lets the player choose it based on system language; FORCED=YES (subtitles) marks captions that must show even when subtitles are off.

EXT-X-I-FRAME-STREAM-INF

#EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=180000,RESOLUTION=1280x720,CODECS="avc1.64001f",URI="v720/iframe.m3u8"

Describes an I-frame-only playlist used for trick-play (fast scrub / thumbnail seeking). The player loads only keyframes when the user drags the scrub bar, which is far cheaper than decoding full segments.

Media playlist tags

EXT-X-TARGETDURATION

#EXT-X-TARGETDURATION:6

The maximum segment duration in the playlist, rounded up to an integer. Required in every media playlist. For live streams it also sets the baseline reload cadence — the player should refetch the playlist roughly every target duration.

EXTINF

#EXTINF:6.006,
v720/seg-00000.m4s

Precedes each segment and gives its exact duration in seconds (the trailing comma is required; an optional title can follow it). These durations are summed to build the timeline and seek bar, so they must match the real media precisely.

EXT-X-MEDIA-SEQUENCE

#EXT-X-MEDIA-SEQUENCE:1024

The sequence number of the first segment in the playlist. For VOD it is usually 0; for live it increments as the sliding window advances, letting the player detect missed or duplicated segments across reloads.

EXT-X-PLAYLIST-TYPE

#EXT-X-PLAYLIST-TYPE:VOD

VOD means the playlist is fixed and fully seekable. EVENT means segments are only ever appended (a live event you can scrub back through). The tag's absence implies a standard sliding-window live stream where old segments are removed.

EXT-X-ENDLIST

#EXT-X-ENDLIST

Marks the end of the playlist. Once a player sees it, it stops reloading the playlist. For live, you transition a stream to VOD-on-demand by appending this tag when the event ends.

EXT-X-MAP

#EXT-X-MAP:URI="v720/init.mp4"

Points at the initialization segment for fMP4/CMAF renditions — the ftyp/moov boxes that configure the decoder. Must be fetched before any media segment, and re-fetched when switching to a rendition with different codec parameters.

EXT-X-KEY

#EXT-X-KEY:METHOD=SAMPLE-AES,URI="skd://drm.example.com/asset-42",KEYFORMAT="com.apple.streamingkeydelivery",KEYFORMATVERSIONS="1"

Declares the encryption applied to subsequent segments. METHOD is NONE, AES-128 (whole-segment), or SAMPLE-AES (sample-level, used by FairPlay and multi-DRM cbcs). URI locates the key or license; IV supplies an explicit initialization vector; KEYFORMAT identifies the DRM system. A later METHOD=NONE line ends encryption — handy for clear ad insertions.

EXT-X-DATERANGE

#EXT-X-DATERANGE:ID="ad-break-3",START-DATE="2026-05-25T18:30:00.000Z",DURATION=30.0,SCTE35-OUT=0xFC30...

Attaches metadata to a point or interval on the timeline — most commonly SCTE-35 ad-break markers, but also chapter and program boundaries. Server-side ad insertion and client-side ad triggering both rely on DATERANGE (or its companion EXT-X-CUE-OUT/EXT-X-CUE-IN tags). See how markers drive ad stitching in the SSAI tool.

A complete annotated media playlist

#EXTM3U
#EXT-X-VERSION:7
#EXT-X-TARGETDURATION:6
#EXT-X-MEDIA-SEQUENCE:0
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-MAP:URI="v720/init.mp4"
#EXT-X-KEY:METHOD=SAMPLE-AES,URI="skd://drm.example.com/a42",KEYFORMAT="com.apple.streamingkeydelivery",KEYFORMATVERSIONS="1"
#EXTINF:6.006,
v720/seg-00000.m4s
#EXTINF:6.006,
v720/seg-00001.m4s
#EXT-X-DATERANGE:ID="ad-1",START-DATE="2026-05-25T18:30:12.012Z",DURATION=15.0,SCTE35-OUT=0xFC30...
#EXTINF:6.006,
v720/seg-00002.m4s
#EXT-X-ENDLIST

Where to go next

Tags are the vocabulary; the manifest internals guide covers the grammar that strings them together. To understand how a player turns the BANDWIDTH values above into switching decisions, read Adaptive Bitrate (ABR) at the Player Level, and to design the variants those tags describe, see Building the Bitrate Ladder.