HTTP Live Streaming

HTTP Live Streaming is an HTTP-based adaptive bitrate streaming communications protocol developed by Apple Inc. and released in 2009. Support for the protocol is widespread in media players, web browsers, mobile devices, and streaming media servers., an annual video industry survey has consistently found it to be the most popular streaming format.
HLS resembles MPEG-DASH in that it works by breaking the overall stream into a sequence of small HTTP-based file downloads, each downloading one short chunk of an overall potentially unbounded transport stream. A list of available streams, encoded at different bit rates, is sent to the client using an extended M3U playlist.
Based on standard HTTP transactions, HTTP Live Streaming can traverse any firewall or proxy server that lets through standard HTTP traffic, unlike UDP-based protocols such as RTP. This also allows content to be offered from conventional HTTP servers and delivered over widely available HTTP-based content delivery networks. The standard also includes a standard encryption mechanism and secure-key distribution using HTTPS, which together provide a simple DRM system. Later versions of the protocol also provide for trick-mode fast-forward and rewind and for integration of subtitles.
Apple has documented HTTP Live Streaming as an Internet Draft, the first stage in the process of publishing it as a Request for Comments. As of December 2015, the authors of that document have requested the RFC Independent Stream Editor to publish the document as an informational RFC outside of the IETF consensus process.
In August 2017, was published to describe version 7 of the protocol.

Architecture

HTTP Live Streaming uses a conventional web server, that implements support for HTTP Live Streaming, to distribute audiovisual content and requires specific software, such as OBS to fit the content into a proper format for transmission in real time over a network.
The service architecture comprises:
;Server
;Distributor
;Client

Features

HTTP Live Streaming provides mechanisms for players to adapt to unreliable network conditions without causing user-visible playback stalling. For example, on an unreliable wireless network, HLS allows the player to use a lower quality video, thus reducing bandwidth usage. HLS videos can be made highly available by providing multiple servers for the same video, allowing the player to swap seamlessly if one of the servers fails.

Adaptability

To enable a player to adapt to the bandwidth of the network, the original video is encoded in several distinct quality levels. The server serves an index, called a master playlist, of these encodings, called variant streams. The player can then choose between the variant streams during playback, changing back and forth seamlessly as network conditions change.

Using fragmented MP4

At WWDC 2016 Apple announced the inclusion of byte-range addressing for fragmented MP4 files, or fMP4, allowing content to be played via HLS without the need to multiplex it into MPEG-2 Transport Stream. The industry considered this as a step towards compatibility between HLS and MPEG-DASH.

Low Latency HLS

Two unrelated HLS extensions with a Low Latency name and corresponding acronym exist:

Apple Low Latency HLS which was announced by Apple at WWDC2019
Community LHLS which predated Apple's publication and is allegedly simpler

The remainder of this section describes Apple's ALHLS. It reduces the glass-to-glass delay when streaming via HLS by reducing the time to start live stream playbacks and maintain that time during a live-streaming event.
It works by adding partial media segment files into the mix, much like MPEG-CMAF's fMP4. Unlike CMAF, ALHLS also supports partial MPEG-2 TS transport files. A partial media segment is a standard segment split into equal segments of less than a second. The standard first segment is replaced by the series of partial segments. Subsequent segments are of the standard size.
HTTP/2 is required to push the segments along with the playlist, reducing the overhead of establishing repeated HTTP/TCP connections.
Other features include:

Playlist Delta Updates: only sending what changed between playlists, which typically fit in a single MTU making it more efficient to load the playlists which, with large DVR windows, can be quite large.
Blocking of playlist reload: when requesting live media playlists, wait until the first segment is also ready, and return both at the same time
Rendition Reports: add metadata to other media renditions to make switching between ABR faster
New tags added: EXT-X-SERVER-CONTROL / EXT-X-PART / EXT-X-SKIP / EXT-X-RENDITION-REPORT
URL QUERY_STRING ?_HLS callbacks added

Apple also added new tools: tsrecompressor produces and encodes a continuous low latency stream of audio and video. The mediastreamsegmenter tool is now available in a low-latency version. It is an HLS segmenter that takes in a UDP/MPEG-TS stream from tsrecompressor and generates a media playlist, including the new tags above.
Support for low-latency HLS is available in tvOS 13 beta, and iOS & iPadOS 14.
On April 30, 2020, Apple added the low latency specifications to the second edition of the main HLS specification.

Dynamic ad insertion

Dynamic ad insertion is supported in HLS using splice information based on SCTE-35 specification. The SCTE-35 splice message is inserted into the media playlist file using the EXT-X-DATERANGE tag. Each SCTE-35 splice_info_section is represented by an EXT-X-DATERANGE tag with a SCTE35-CMD attribute. A SCTE-35 splice out/in pair signaled by the splice_insert commands is represented by one or more EXT-X-DATERANGE tags carrying the same ID attribute. The SCTE-35 splice out command should have the SCTE35-OUT attribute and the splice in command should have the SCTE35-IN attribute.
Between the two EXT-X-DATERANGE tags that contain the SCTE35-OUT and SCTE35-IN attributes respectively, there may be a sequence of media segment URIs. These media segments normally represent ad programs that can be replaced by the local or customized ad. The ad replacement does not require the replacement of the media files, only the URIs in the playlist need to be changed to point to different ad programs. The ad replacement can be done on the origin server or on the client's media-playing device.

Server implementations

Notable server implementations supporting HTTP Live Streaming include:

Adobe Media Server supports HLS for iOS devices and Protected HTTP Live Streaming.
Akamai supports HLS for live and on-demand streams.
AT&T supports HLS in all formats live or on-demand.
Ant Media Server support HLS and Low Latency HLS for live and on-demand streams.
Axis Communication IP cameras supports HLS via App ACAP
Instart supports HLS for on-demand streams.
Amazon CloudFront supports HLS for on-demand streams.
Bitmovin supports HLS for on-demand and live streaming.
CDNetworks supports HLS for live and on-demand streams.
Cisco Systems: supports full end-to-end delivery for Live/TSTV/VOD/HLS and Cloud DVR services.
Cloudflare supports HLS for live and on-demand streams.
EdgeCast Networks supports cross-device streaming using HLS.
Fastly supports HLS for live and on-demand streams.
Helix Universal Server from RealNetworks supports iPhone OS 3.0 and later for live and on-demand HTTP Live or On-Demand streaming of H.264 and AAC content to iPhone, iPad and iPod.
IIS Media Services from Microsoft supports live and on-demand Smooth Streaming and HTTP Live Streaming.
Level 3 supports HLS live and on-demand streams.
Limelight Networks supports HLS for some accounts.
Nginx with the nginx-rtmp-module supports HLS in live mode. Commercial version Nginx Plus, which includes ngx_http_hls_module module, also supports HLS/HDS VOD.
Nimble Streamer supports HLS in live and VOD mode, Apple Low Latency HLS spec is also supported.
Node.js with the hls-server package supports hls encoding to live mode and local files conversion.
OvenMediaEngine is an open source project that supports Low Latency HLS and HLS for live streaming.
PeerTube supports HLS
Storm Streaming Server supports HLS as backup mode for its Media Source Extensions player
Tata Communications CDN supports HLS for live and on-demand streams.
TVersity supports HLS in conjunction with on-the-fly transcoding for playback of any video content on iOS devices.
Ustream supports HLS delivery of live broadcasts. The ingested stream is re-transcoded if the original audio and video codec falls outside HLS requirements.
VLC Media Player supports HLS for serving live and on-demand streams as of version 2.0.
Wowza Streaming Engine from Wowza Media Systems supports HLS and encrypted HLS for live, on-demand streaming and Apple Low Latency HLS spec.

Usage

Google added HTTP Live Streaming support in Android 3.0.
HP added HTTP Live Streaming support in webOS 3.0.5.
Microsoft added support for HTTP Live Streaming in EdgeHTML rendering engine in Windows 10 in 2015.
Microsoft added support for HTTP Live Streaming in IIS Media Services 4.0.
Yospace added HTTP Live Streaming support in Yospace HLS Player and SDK for flash version 1.0.
Sling Media added HTTP Live Streaming support to its Slingboxes and its SlingPlayer apps.
In 2014/15, the BBC introduced HLS-AAC streams for its live internet radio and on-demand audio services, and supports those streams with its iPlayer Radio clients.
Twitch uses HTTP Live Streaming to transmit and scale the live streaming to many concurrent viewers, also supporting multiple variants.

Supported players and servers

HTTP Live Streaming is natively supported in the following operating systems:

Windows 10 version 1507 to 2004
Windows 11 Media Player
macOS 10.6+
iOS 3.0+
Android 4.1+

Windows 10 used to have native support for HTTP Live Streaming in EdgeHTML, a proprietary browser engine that was used in Microsoft Edge before the transition to the Chromium-based Blink browser engine. Edge Legacy was included in Windows 10 up till version 2004. It was replaced by Edge Chromium in version 20H2. Along with Windows 11, Microsoft released an updated Media Player that supports HLS natively.

Clients

Client	Platform	Live Streaming	DRM	As of Version	Editor
Safari (web browser)	macOS, iOS			6.0+ Has full HLS support.	Apple
Microsoft Edge	Windows 10			Supported natively on Edge Legacy's engine EdgeHTML from version 12 to 18. No native support on Edge Chromium from version 79 to present.	Microsoft
Google Chrome / Chromium	Windows, macOS, Linux, Android, iOS			30+ Android and iOS have OS-dependent native support. Other platforms require Media Source Extensions.	Google
Firefox	Windows, macOS, Linux, Android, iOS			50.0+ for Android and 57.0 for others, 59.0 has enhanced support for Android Other platforms require Media Source Extensions.	Mozilla
QuickTime Player	macOS			10.0+ Has full HLS support.	Apple
iTunes	Windows, macOS			10.1+ Has full HLS support. To play a HLS stream, go to File > Open Stream and replace "http://" with "itls://" or "itals://" in the stream URL.	Apple
Media Player (2022)">Media Player (Windows 11)">Media Player (2022)	Windows 10, Windows 11			Does not include the original Win32 version of Windows Media Player.	Microsoft
StreamS HiFi Radio	iOS, tvOS iPhone, iPad, and AppleTV			7.3+ Plays Internet Radio Streams HLS Audio - 100% Compliant AAC-LC/HE-AAC/xHE-AAC 2.0 Stereo/5.1-7.1 Surround ES - Elementary Stream ADTS fMP4 - Fragmented ISO MP4 Displays Synchronous Realtime Metadata and Graphics	StreamS/Modulation Index LLC
VLC media player	Windows, macOS, Linux, Android, iOS, Windows Phone			VLC 2.x has partial support up to HLS version 3. VLC 3.0 has full HLS support.	VideoLAN
Media Player Classic Home Cinema	Windows				Gabest, Doom9 forum users
PotPlayer	Windows				Daum Communications
MPlayer / SMPlayer / mpv (media player)	Windows, macOS, Linux, BSD				Ricardo Villalba
GOM Player	Windows				Gretech
Cameleon	Windows, macOS				Yatko
Audacious (software)	Windows, Linux				Audacious
Radio Tray	Linux				Carlos Ribeiro
Kodi (software)	Windows, macOS, Linux, Android, iOS			12.0 Alpha 5 and later DRM support requires a monthly/nightly build	XBMC Foundation
MythTV	Windows, macOS, Linux, FreeBSD			0.26	MythTV
JRiver Media Center	Windows, macOS				JRiver
XiiaLive	Android, iOS			3.0+ Plays internet radio streams.	Visual Blasters LLC
Tunein radio	Android, iOS			3.3+ Plays internet radio streams.	TuneIn
myTuner Radio	Android, iOS, Windows Phone, Windows 8, macOS			Plays internet radio streams.	AppGeneration Software
Internet Radio Player	Android			Plays internet radio streams.	MuserTech
GuguRadio	iOS			Plays internet radio streams.	Leon Fan
AIMP	Windows, Android			4.10+ Plays internet radio streams.	Artem Izmaylov
Mini Stream Player	Android				JogiApp
MX Player	Android				J2 Interactive
TV Streams	macOS, iOS, tvOS			v7.1	Tiago Martinho
HP Touchpad	WebOS			3.0.5	HP
Amino x4x STB	Amino set-top boxes			2.5.2 Aminet	Aminocom.com
Dune HD TV	Dune HD set-top boxes			TV series	dunehd.com
CTU Systems Ltd	CTU Systems Ltd Eludo Play Out System			TV series	ctusystems.com
nangu.TV	Motorola set-top boxes			2.0	nangu.TV
Roku Digital Video Player	Roku set-top boxes			Roku OS / SDK 2.6	Roku
Telebreeze Player	HTML, Android, iOS, Windows, MacOS, Roku, MAG Infomir, Samsung Tizen, LG WebOS, Google Chromecast, tvOS, Amazon Fire TV, AndroidTV				Telebreeze
bitdash	HTML5 or Flash, Web and Mobile			Version 3.0+	bitmovin
3ivx	Windows 8, Windows Phone 8 & Xbox One			2.0	3ivx
THEOplayer	HTML5, SDK				THEO Technologies
OvenPlayer	HTML5			0.10.0+	AirenSoft
Viblast Player	HTML5, iOS, Android				Viblast Ltd
Flowplayer	Adobe Flash, iOS, Android, HTML5			The Flash HLS plugin is available from GitHub.	Flowplayer Ltd
JW Player	Adobe Flash, iOS, Android, HTML5			HLS is provided in all JW Player versions as of JW8	JW Player
Radiant Media Player	Adobe Flash, HTML5			1.5.0	Radiant Media Player
Yospace	Adobe Flash			2.1	Yospace
Onlinelib	Adobe Flash			2.0	Onlinelib.de
VODOBOX HLS Player	Adobe Flash, HTML5, iOS, Android				Vodobox
NexPlayer	HTML5, Android, iOS, Chromecast, Windows, Mac, Linux, Tizen, WebOS				NexStreaming
ffplay/avplay					FFmpeg/Libav
GPAC				0.5.0	Telecom ParisTech inc.
QuickPlayer	Android, iOS, Windows 7, 8, 8,1 and 10				Squadeo
hls.js	MSE Browsers				Dailymotion open source
hasplayer.js	MSE Browsers				open source
Hola Player	HTML5, Adobe Flash, iOS, Android			All versions	Hola Ltd open source
Shaka Player	HTML5			2.1	Open Source
Fluid Player	HTML5			2.2.0+	Fluid Player OSS
Video.js	MSE Browsers. Flash with flashls source handler fallback.				Open source
foobar2000	Windows			1.6.1	Peter Pawłowski
QMPlay2	Windows, macOS, Linux			It has VU meters and a spectrum analyzer	Open source

Servers

Product	Technology	As Of Version	Editor	Free	Notes
ANEVIA Genova Live	Bundled software for transcoding to H.264 & HEVC, and packaging to HLS, MPEG-DASH, Microsoft [Smooth Streaming Protocol\|MS Smooth Streaming]		Anevia
AvProxy	Light software for live streaming Input and output streams : HTTP, HLS/AES-128, UDP, RTP, MPTS demux	2.19			Proprietary but free for use
bitcodin		SaaS	bitmovin
VLC		1.2
Video Cloud		SaaS	Brightcove
IIS Media Services		4.0	Microsoft
Antik Media Streamer	Ingest Module, Stream replication UDP/HTTP, HLS streaming, Video archive with snapshots, Server-side Timeshift, time zone shifting with multiple time zones, Stream Encryption using AES and key-rotation	3.0	Antik technology
Adobe Media Server	Live and VOD streaming as origin and edge server	5.0	Adobe
Ant Media Server	Supports HLS and Low Latency HLS in standalone and cluster modes. It can ingest WebRTC, RTMP, RTSP and can create HLS and Low Latency HLS playback endpoints	2.11	Ant Media		HLS is a out of the box feature in Community and Enterprise Editions. Low Latency HLS is a plugin that is compatible in Community and Enterprise Editions.
Evostream Media Server	Cross-platform including embedded systems such as encoders, IP cameras, DVRs, and more. Supports: Adobe Flash RTMP, RTMPS, LiveFLV, full transcoder for creating lower bitrate streams, HTTP Live Streaming for streaming to iPhones, iPads and Androids, HTTP Dynamic Streaming for Adobe Air, Microsoft Smooth Streaming for Microsoft devices, RTSP with RTP or MPEG-TS, MPEG-TS, compatible Live Encoding, strong security for your content, built-in clustering mechanism and more.	1.6.5	EvoStream
MythTV		0.25	MythTV
MACNETIX VOD-Server		3.0	MACNETIX
Anevia NEA Live Servers	Transcapsulation: from one input, several outputs		Anevia
Packet Ship OverView:Origin Server	Capture from IPTV multicast and chunking to HLS for multi-bandwidth live streams, with AES encryption	2.1	Packet Ship
nangu.TV Streamers	on-the-fly adaptation: content is stored once enabling several outputs		nangu.TV
TVersity Media Server		1.9	TVersity		Pro Edition only
Helix Universal Server	Live + VOD HLS with Verimatrix DRM integration, ABR, Multi-Resolution, AES encryption	15.0+	RealNetworks		High performance HLS
Wowza Streaming Engine	Live and VOD streaming as origin and edge server with DVR, DRM Integration and Transcoding for adaptive delivery. Outputs to MPEG-DASH, HLS, HDS, Smooth Streaming, RTMP, and RTSP. Supports Apple Low Latency HLS.	2.0+	Wowza Media Systems
Unified Streaming Platform	Muxes media content from one unified source to multiple outputs		Unified Streaming
VODOBOX Live Server	Outputs HTTP Live Streaming with Adaptive bitrate streaming. Video codecs : AVC H.264 / HEVC H.265 Audio codecs : MP3 / AAC Transport layers : HTTP / FTP / Amazon AWS S3 / Microsoft Azure Web Storage / writing to disk Hostings : internal HTTP Web server and/or external Web servers	1.0	Vodobox		Supports input live streams from DVB-T devices, satellite receivers, IP streams, Microsoft DirectShow drivers. Encoder is compliant with Intel Quick Sync Video and Nvidia NVENC hardware acceleration.
Flixwagon Platform Video Server			Flixwagon
StreamCoder Live Encoder	Realtime video encoder. Supports multi-bitrates and multi-languages		Ektacom
Apache HTTP Server			Apache Software Foundation
Unreal Media Server		9.5	Unreal Streaming Technologies		Latency of live streams can be as low as 2.5 seconds over the Internet
Nimble Streamer	RTMP / RTSP / Icecast / MPEG-TS to ABR HLS. MP4 / MP3 to VOD HLS. Apple Low Latency HLS spec is supported.	1.0.0-x	WMSPanel
Nginx-rtmp-module	Free module for nginx server with support of HLS live streaming. Compliant with iOS and Android.	0.9.x	Roman Arutyunyan
Nginx Plus	VOD HLS as origin		NGINX, Inc.
OvenMediaEngine	Supports Low Latency HLS, HLS, ABR LL-HLS, and ABR HLS for live streaming	0.16.0+	AirenSoft		GNU Affero General Public License
Flussonic Media Server	Multi-platform support for HTTP, RTSP, RTMP, DASH, Time Shifting, DVR Functions with Unlimited Rewind Capabilities HLS streaming specific to iOS platform support.	3.0+	Flussonic, LLC.		Supporting a magnitude of features with full HTTP support.
VBrick Distributed Media Engine		2.0	VBrick Systems, Inc.		Live and stored HLS. Live can be transmuxed from several input mux including RTP, RTMP, and MPEG-TS using H.264 encoding
Telebreeze Coder / Media Server	Input streams and interfaces: UDP, TCP, RTP, HLS, HTTP, RTMP Output Streams: HLS, HTTP, UDP Preprocessing: Resize, Deinterlace, Frame Rate Conversion, Audio Resampling, Logo Rendering		Telebreeze
LEADTOOLS Media Streaming Server SDK	Converts files on the fly to Adobe HDS, Apple HLS, MPEG-DASH, Microsoft Smooth Streaming, RTSP.	19.0	LEAD Technologies
MC-ROUTE	Multifunctional software for live stream routing and protocol conversion	4.4	Teracue		Supported protocols: TS over UDP, RTP, TCP, HLS, HTTP, RTSP/RTP
Direkt router	Live hardware decoder with SDI, NDI out and transcoding	4.1	Intinor		Supported protocols in: TS over UDP, RTP, TCP, HLS, HTTP, RTMP out: UDP, RTP, TCP, RTMP
Elecard CodecWorks	Professional platform for real-time encoding and transcoding into HEVC/H.265, AVC/H.264 and MPEG-2 video supporting adaptive bitrate streaming via HLS and MPEG-DASH protocols.	4.6	Elecard		Supported protocols: TS over UDP/RTP/SRT, RTMP Output, HLS, MPEG-DASH output, UDP/RTP/SRT, NDI
TAC - Teracue Application Cloud	Professional stream routing and real-time encoding/transcoding platform supporting various audio and video codec and streaming protocols	1.0	Teracue		Supported protocols IN and OUT: UDP, RTP, RTSP, RTMP, TCP, HLS, HTTP, FEC, SRT Supported protocols IN only: SDVoE and NDI
Peertube	A free and open-source, decentralized, ActivityPub federated video platform using HLS peer-to-peer technology to reduce load on individual servers when viewing videos.	1.3.0			Videos are made available via HTTP to download, but playback favors a peer-to-peer playback using HLS.