M3U8
The text index a player reads before any HLS stream. It weighs a few kilobytes, holds no video, and nothing plays without it.
An M3U8 is the playlist of an HLS stream: a text file listing the quality levels and the video segments of each. It is not the video. It is the manifest that guides the player, and on protected delivery its link expires.
What is an M3U8 file?
An M3U8 is an index file that describes a streaming video: it lists every available quality level and the addresses of the short segments that make up each one. When a player starts an adaptive stream, the manifestManifestA small index file (.m3u8 or .mpd) that lists every available rendition and segment so the player knows what it can request.Open definition → is the first thing it downloads.
The most common mix-up is to think the .m3u8 is the video. The footage is split into tens or hundreds of segments, and the manifest is the light text that tells the player they exist, which quality each one is and in what order to play them. The name comes from the M3U audio playlist format, with the “8” for UTF-8 encoding — which is why an .m3u8 opens in any text editor.
What is inside
Lists each version once, with the bandwidth it needs, the resolutionResolutionThe pixel dimensions of a video frame — 480p, 720p, 1080p, 2160p (4K). Determines how sharp the picture looks on a given screen.Open definition → and the codecsCodecThe algorithm that compresses and decompresses video — H.264, H.265 (HEVC) and AV1 are the most common in modern streaming.Open definition →. It can also point to alternative audio and subtitle tracks.
One per version. Lists that version’s segments in order, with each duration and, on an encrypted stream, a pointer to the key.
The player fetches the master, picks the version that fits the measured bandwidth, fetches that media playlist and starts requesting segments. When the connection changes it jumps to another version at the next segment — that is adaptive bitrateAdaptive Bitrate (ABR)Automatically adjusts video quality in real time to match each viewer’s connection speed — smooth playback from 480p to 4K with no buffering.Open definition →.
M3U8 and MPD
| Format | Protocol | Type | Structure |
|---|---|---|---|
| .m3u8 | HLSHLS (HTTP Live Streaming)Apple’s adaptive streaming protocol. Uses .m3u8 manifests and segmented delivery; supported on every browser, device and smart TV.Open definition → | Plain text | Master playlist → media playlists |
| .mpd | DASHDASHDynamic Adaptive Streaming over HTTP — an open ISO standard using .mpd manifests, common for DRM-protected premium content.Open definition → | XML | A single Media Presentation Description |
Modern platforms usually generate both from the same segments to cover every device.
How to open an .m3u8
Under Media → Open Network Stream, paste the .m3u8 address. VLC reads the playlist and plays the segments.
Plays HLS natively on Mac, iPhone and iPad: just open the link.
Need a web player with HLS support inside the page, like the one any video platform provides.
Why a copied .m3u8 link stops working
On protected delivery the address is not permanent. It is a signed URLSigned URLA playback link carrying an expiry and a cryptographic token — it stops working once the window closes, and a tampered link never works.Open definition →: it carries a signature and an expiry, and the delivery layer checks both before serving anything. After the expiry the video is still there, but the map to it is gone. If the content also uses DRMDRMEncryption of the video file plus a licence server that issues a per-session key — so a downloaded copy stays unplayable.Open definition →, the segments are encrypted and will not play without a licence.
Further reading
- Apple — HTTP Live Streaming — the HLS playlist specification.
- Manifest — the general concept, with .m3u8 and .mpd.
