#EXT-X-VERSION Explained: The HLS Compatibility Attribute That Controls What a Playlist Can Use

Every HLS playlist is a plain-text file built around a small set of tags. Most tags are straightforward — #EXTINF marks a segment duration, #EXT-X-ENDLIST closes a VOD playlist. But one tag quietly controls which other tags are even allowed to appear: #EXT-X-VERSION.

What the Version Tag Declares

#EXT-X-VERSION:<n> declares the minimum integer version of the HLS specification that a parser must implement to read this playlist correctly. It appears at most once, anywhere in the file before any media segment URI, and its value is a positive integer starting at 1.

The tag doesn't describe the encoder that produced the playlist or the server that serves it. It describes the reader: if your parser doesn't support version n, do not attempt to parse this playlist.

Why Omitting It Means Version 1

The spec says a missing #EXT-X-VERSION tag implies version 1. Version 1 is the baseline: integer EXTINF durations, one URI per segment, no byte ranges, no IV on key tags, no I-frame playlists. In practice, almost every streaming platform uses at least version 3 (floating-point durations), so a real-world playlist that omits the tag but uses decimal EXTINF values is already violating the spec. Parsers typically handle this by treating absent as version 3 when they encounter a decimal duration.

What Each Version Unlocks

Each version adds a specific set of new tags or attributes:

• Version 2 — Added the IV attribute to #EXT-X-KEY, enabling per-segment initialization vectors for AES-128 encryption.
• Version 3 — Introduced floating-point #EXTINF durations (e.g., 6.006 instead of 6). This is the version the vast majority of streams use.
• Version 4 — Added #EXT-X-BYTERANGE (address multiple segments inside one file using HTTP Range) and #EXT-X-I-FRAMES-ONLY (I-frame trick-play playlists).
• Version 5 — Unlocked KEYFORMAT and KEYFORMATVERSIONS on #EXT-X-KEY, required for SAMPLE-AES encryption used in FairPlay DRM.
• Version 6 — Deprecated #EXT-X-ALLOW-CACHE and allowed #EXT-X-MAP in I-frames-only playlists.
• Version 7 — Added #EXT-X-SESSION-DATA and #EXT-X-SESSION-KEY to master playlists for session-level metadata and pre-positioned DRM keys.

How a Parser Breaks When It Ignores the Version Tag

A parser that skips #EXT-X-VERSIONand encounters version-3 floating-point durations where it expects integers will either truncate them (treating a 6.006-second segment as 6 seconds) or fail on the decimal point. Truncated durations shift every subsequent segment's timestamp by a few milliseconds — harmless in isolation but compounding across hundreds of segments in a long recording, producing a file whose audio drifts out of sync with the video.

A version-5 KEYFORMAT="com.apple.streamingkeydelivery"attribute on an EXT-X-KEY tag is silently ignored by a parser that doesn't understand it — which means the stream is treated as unencrypted when it isn't, producing garbled or failing decryption at playback.

Version-4 byte-range segments are a subtler failure. A parser that doesn't implement #EXT-X-BYTERANGEwill try to download the full backing file as a single segment instead of issuing a ranged HTTP request for the bytes it actually needs. The downloaded data will be wrong, and the output file will be corrupted. This failure is silent — there's no error, the file just doesn't play correctly.

How This Site's Converter Handles It

The converter in /convert reads #EXT-X-VERSIONon the first pass and uses it to decide which tags to attempt to parse and which to treat as unknown. Unknown tags from future versions are silently skipped rather than treated as parse errors — so a version-8 playlist with a tag the parser has never seen won't crash the download. It will simply ignore the unrecognized line and proceed with the segments it does understand.

The extension's M3U8 detection heuristic checks for the mandatory #EXTM3U header rather than the version tag, since the version is optional and the M3U8 marker is not. A playlist without a version tag is still a valid M3U8 file; a playlist without the #EXTM3U header is not.

Version Compatibility in Practice

For most HLS downloads, version handling is invisible — nearly every live and VOD stream in the wild is version 3 or 4, and all the relevant segment and key tags at those versions have been stable for years. You're unlikely to encounter a version-6 or version-7 feature unless you're recording from a platform that uses I-frame trick-play playlists or session-level DRM metadata.

Where version matters most is in byte-range segments (version 4). A converter that doesn't implement #EXT-X-BYTERANGE will download the wrong bytes without any visible error. The /convert route handles byte-range requests correctly by passing the Range header through the extension bridge, which forwards it as a real HTTP Range request to the CDN.

Try It

If you have an HLS stream you want to save, the Stream Video Downloader extension detects M3U8 playlists on any page and handles version-specific playlist features automatically. Click Convert to download any variant as an MP4 file, no transcoding required.