Manifest file
A manifest file in video streaming is a small text file that tells the player which versions of a video exist and where to find each segment. It lists quality levels, audio and subtitle tracks, segment URLs and timing. HLS uses M3U8 manifests and MPEG-DASH uses MPD manifests. The player reads the manifest before downloading any video.
Why it matters
The manifest controls what every viewer can see and how playback adapts. It decides which qualities, languages and ad breaks are offered. A broken or slow manifest stops playback for everyone, so it is a small file with large business impact.
How it works
- After encoding, a packager writes a manifest listing every quality level, audio track and subtitle track.
- The player downloads the manifest first, before any video.
- It picks a starting quality level based on screen size and measured bandwidth.
- It then requests segments in order, switching levels as conditions change; live manifests refresh regularly.
What is the difference between a master playlist and a media playlist?
A master playlist lists all available quality levels and tracks, while a media playlist lists the actual segments for one of them. In HLS, the player loads the master playlist first, picks a level, then loads that level's media playlist. DASH puts both kinds of information in a single MPD file.
Why does my HLS manifest return a 404 error?
A 404 on an HLS manifest usually means the URL is wrong, the stream has not started, or the file expired or was removed. For live streams, the manifest may not exist until the encoder connects. Signed URLs that have expired and CDN cache rules can also cause 404 or 403 errors.
Where it's used
OTT services use manifests to offer 4K only on premium plans and to list audio languages per title, while live sports streamers insert ad breaks into the manifest during games. For scheduled linear channels, FastPix Cloud Playout supports SCTE-35 markers, the cues that tell ad systems where those breaks go.
By the numbers
- Apple recommends that HLS target durations be 6 seconds, and media segments must not exceed the target duration by more than 0.5 seconds. (HLS Authoring Specification for Apple Devices)
