Adaptive bitrate streaming is a technique used in streaming multimedia over computer networks.
While in the past most video or audio streaming technologies utilized packetized, stateful, single-bitrate streaming protocols such as RTP with RTSP, today's adaptive streaming technologies are based almost exclusively on HTTP, and are designed to work efficiently over large distributed HTTP networks.
Adaptive bitrate streaming works by detecting a user's bandwidth, CPU capability, as well as device type (such as smartphone, desktop computer, or smart TV) in real time, adjusting the quality of the media stream accordingly. It requires the use of an encoder which encodes a single source media (video or audio) at multiple bit rates. The player client switches between streaming the different encodings depending on available resources. This results in providing very little buffering, faster start times and a good experience for both high-end and low-end connections.
More specifically, adaptive bitrate streaming is a method of video streaming over HTTP where the source content is encoded at multiple bit rates. Each of the different bit rate streams are segmented into small multi-second parts. First, the client downloads a manifest file that describes the available stream segments and their respective bit rates. During stream start-up, the client usually requests the segments from the lowest bit rate stream. If the client finds that the network throughput is greater than the bit rate of the downloaded segment, then it will request a higher bit rate segment. Later, if the client finds that the network throughput has deteriorated, it will request a lower bit rate segment. An adaptive bitrate (ABR) algorithm in the client performs the key function of deciding which bit rate segments to download, based on the current state of the network. Several types of ABR algorithms are in commercial use: throughput-based algorithms use the throughput achieved in recent prior downloads for decision-making (e.g., throughput rule in dash.js), buffer-based algorithms use only the client's current buffer level (e.g., BOLA in dash.js), and hybrid algorithms combine both types of information (e.g., DYNAMIC in dash.js).
Current uses Video streaming services that need to distribute content live or on-demand over the public Internet (also known as over-the-top media services) use adaptive bitrate technology in order to provide consumers with highest quality experience while minimizing buffering interruptions. When distributed over HTTP using content delivery networks adaptive bitrate streaming can easily be scaled to support streaming video content to millions of viewers concurrently. The world's largest streaming services, such as those operated by Netflix, Disney, NBC Universal, Warner Bros. Discovery, Apple, Google, Amazon and others, have all been actively using adaptive bit rate technology for many years now, making it standard practice for high-end streaming providers.
Benefits of adaptive bitrate streaming
Traditional server-driven adaptive bitrate streaming provides consumers of streaming media with the best-possible experience, since the media server automatically adapts to any changes in each user's network and playback conditions. The media and entertainment industry also benefit from adaptive bitrate streaming. As the video space grows, content delivery networks and video providers can provide customers with a superior viewing experience. Adaptive bitrate technology requires additional encoding, but simplifies the overall workflow and creates better results.
HTTP-based adaptive bitrate streaming technologies yield additional benefits over traditional server-driven adaptive bitrate streaming. First, since the streaming technology is built on top of HTTP, contrary to RTP-based adaptive streaming, the packets have no difficulties traversing firewalls and NAT devices. Second, since HTTP streaming is purely client-driven, all adaptation logic resides at the client. This reduces the requirement of persistent connections between server and client application. Furthermore, the server is not required to maintain session state information on each client, increasing scalability. Finally, existing HTTP delivery infrastructure, such as HTTP caches and servers, can be seamlessly adopted.
A scalable CDN is used to deliver media streaming to an Internet audience. The CDN receives the stream from the source at its Origin server, then replicates it to many or all of its Edge cache servers. The end-user requests the stream and is redirected to the "closest" Edge server. This can be tested using libdashlibdash: Open-source DASH client library by bitmovin and the Distributed DASH (D-DASH) dataset, which has several mirrors across Europe, Asia and the US. The use of HTTP-based adaptive streaming allows the Edge server to run a simple HTTP server software, whose license cost is cheap or free, reducing software licensing cost, compared to costly media server licences (e.g., Adobe Flash Media Streaming Server). The CDN cost for HTTP streaming media is then similar to HTTP web caching CDN cost.
History
Non-adaptive segmented media delivery over HTTP DVD Forum created a WG1 Special Streaming group in October 2002 that was co-chaired by Toshiba and Phoenix Technologies, with participation from Microsoft, Apple Computer, DTS Inc., Warner Brothers, 20th Century Fox, Digital Deluxe, Disney, Macromedia and Akamai. The group was responsible for developing and standardizing methods of DVD content online delivery, known as DVDoverIP, that would form an integral part of the Enhanced DVD Format specification (DVD-ENAV). One of the specified DVD-ENAV streaming methods described packing MPEG-1 and MPEG-2 DVD TS Sectors into small 2 KB files which could be served to the player using an HTTP server. The MPEG-1 segments represented a lower bandwidth stream, while the MPEG-2 segments represented a higher bit rate stream. An accompanying XML schema provided a simple playlist of bit rates, languages and URL servers. However, the specification did not suggest or define dynamic bitrate switching.
An early HTTP web server based streaming system called SProxy was developed and deployed in the Hewlett-Packard Laboratories in 2006. It showed how to use HTTP range requests to break the content into small segments. SProxy demonstrated the effectiveness of segment-based streaming, gaining the best Internet penetration due to the wide deployment of firewalls, and reducing the unnecessary traffic transmission if a user chooses to terminate the streaming session earlier before reaching the end.
Move Networks Modern adaptive bitrate streaming over HTTP was developed by Move Networks between 2004 and 2006, and started gaining worldwide attention in 2007 when it was chosen by ABC Networks as the streaming solution for their new HD video streaming website. Originally named Quantum Streaming, the ABR technology was incorporated into a suite of products named Move Media Services which included Move Simulcode (video encoding), Move Publish (content publishing, storage and digital rights management), Move Play (player) and Move Monetize (viewing data analytics). Move Networks ABR technology was described in a NAB weekly technology newsletter as follows:
In October 2010, Move Networks was awarded a patent for its adaptive bitrate streaming invention (US patent no. 7818444), based on a provisional patent application filed in April 2004.
Implementations After Move Networks' successfully demonstrated that HTTP-based ABR streaming was a viable commercial alternative to traditional packetized streaming protocols, other implementations of HTTP-based ABR followed shortly: Microsoft demonstrated a prototype of ABR streaming on NBC's Olympics website in August 2008 during the 2008 Summer Olympics. After officially announcing an ABR streaming product in October 2008 at the Digital Hollywood conference it released Smooth Streaming (MSS) as an extension for IIS7 web servers in February (beta) and April (GA) 2009. Apple Inc. first released HTTP Live Streaming (HLS) in June 2009 with the rollout of iOS 3.0 and iPhone 3GS. Adobe Systems released HTTP Dynamic Streaming (HDS) in June 2010. MPEG published the first version of the Dynamic Adaptive Streaming over HTTP (DASH) standard in April 2012, though the work on the standard had begun several years earlier with participation from Microsoft, Apple, Adobe, Netflix and other companies.
Of the ABR streaming implementations described here the only ones still actively developed and used in 2026 are Apple HLS and MPEG DASH.
Microsoft Smooth Streaming (MSS) Smooth Streaming was developed as an IIS Media Services extension that enabled adaptive streaming of media to clients over HTTP. The media storage format was based on the ISO base media file format and published by Microsoft as the Protected Interoperable File Format specification. Microsoft was actively involved with 3GPP, MPEG and DECE organizations' efforts to standardize adaptive bit-rate HTTP streaming, which ultimately resulted in the publication of the DASH standard. Microsoft provided Smooth Streaming Client software development kits for Silverlight and Windows Phone 7, as well as a Smooth Streaming Porting Kit that could be used for other client operating systems, such as Apple iOS, Android, and Linux. IIS Media Services 4.0, released in November 2010, introduced a feature which enabled Live Smooth Streaming H.264/AAC videos to be dynamically repackaged into the Apple HTTP Adaptive Streaming format and delivered to iOS devices without the need for re-encoding. Between 2009 and 2013, Microsoft successfully demonstrated delivery of both live and on-demand 1080p HD video with Smooth Streaming to Silverlight clients. In 2010, Microsoft also partnered with NVIDIA to demonstrate live streaming of 1080p stereoscopic 3D video to PCs equipped with NVIDIA 3D Vision technology.
In 2013 Microsoft shifted its media services product offering to the cloud where it continued to support Smooth Streaming as a core component of Azure Media Services. However, development and adoption of MPEG DASH and HLS as industry standards gradually displaced Smooth Streaming as Microsoft's preferred adaptive streaming technology by the end of that decade. In June 2023 Microsoft announced the retirement of Azure Media Services, effective June 2024, and while the announcement didn't explicitly mention Smooth Streaming by name it effectively meant the end of support for Smooth Streaming in any active Microsoft products.
Apple HTTP Live Streaming (HLS)
HTTP Live Streaming (HLS) is an HTTP-based media streaming communications protocol implemented by Apple Inc. as part of QuickTime X and iOS. HLS supports both live and video on demand content. It works by breaking down media streams or files into short pieces (media segments), which are stored as MPEG-TS or fragmented MP4 files. This is typically done at multiple bitrates using a stream or file segmenter application, also known as a packager. One such segmenter implementation is provided by Apple. Additional packagers are available, including free and open source offerings like Google's Shaka Packager and various commercial tools as well - such as Unified Streaming. The segmenter is also responsible for producing a set of playlist files in the M3U8 format which describe the media chunks. Each playlist is specific to a given bitrate and contains the relative or absolute URLs to the chunks for that bitrate. The client is then responsible for requesting the appropriate playlist depending on available bandwidth.
HTTP Live Streaming is a standard feature in the iPhone 3.0 and newer versions.