Standards for Web Applications on Mobile: current state and roadmap

Latest version: http://www.w3.org/Mobile/mobile-web-app-state/
This version: http://www.w3.org/2015/05/mobile-web-app-state/ (PDF version)
Previous version: http://www.w3.org/2015/01/mobile-web-app-state/

Web technologies have become powerful enough that they are used to build full-featured applications; this has been true for many years in the desktop and laptop computer realm, but is increasingly so on mobile devices as well.

This document summarizes the various technologies developed in W3C that increase the capabilities of Web applications, and how they apply more specifically to the mobile context. A good subset of these technologies are described and explained in the W3C on-line training on programming Web applications.

Core Web Design and Development
Media and Real-Time Communications
Usability and Accessibility
Device Interaction
Network Integration
Application Lifecyle
Payment and Services
Performance & Tuning
Security & Privacy

Status and changes

This document is the 17th edition of this overview of mobile Web applications technologies. The previous edition was released in January 2015. A live version of this document accepts contributions on the W3C Web and Mobile Interest Group Github repository.

This document is published by the Web and Mobile Interest Group; feedback on every aspect of this document should be sent to public-web-mobile@w3.org, the publicly archived mailing list of the interest group, or raised as issues on the Github repository, or alternatively to the author (dom@w3.org). It will serve as input for the next iteration of the document.

The following changes in the Web platform since January 2015 are documented in this udpate:

Published as First Public Working Draft

the audio ouput devices API which lets orient audio streams to different output devices was published as a First Public Working Draft in February;
the Presentation API, a critical component in enabling second-screen experiences, was released as First Public Working Draft in February;
the WAI WCAG and UAAG Working Groups released their mapping of accessibility guidelines to mobile as a Fist Public Working Draft in February;
the credential management API that lets Web applications interact with browser-stored user credentials, was published as First Public Working Draft in April;
the Permissions API which exposes what permissions the user has or has not granted to the Web app, was published as First Public Working Draft in April;
The Web Payments Interest Group published a First Public Working Draft of their payment use cases in April;

Published as Last Call Working Draft

the Media Capture and Streams specification that brings audio and video from cameras and microphones to Web applications was published as a Last Call Working Draft in April;

Returned to Working Draft

the canvas API, previously published as a Candidate Recommendation, returned to Last Call Working Draft status to reflect changes brought to its accessibility features;

Reached Candidate Recommendation

the Web Notifications API that lets Web apps notify theirs users using the underlying OS notification system, was released as a Candidate Recommendation;

Specification merged, split or abandoned

the work started on an NFC API in the NFC Working Group has been abandonned, while new work on browser-compatible approach to NFC has started in the Web NFC Community Group;

Newly tracked

the Geolocation Working Group released an editors draft of their proposed Geofencing API.

Document structure

The features that these technologies add to the Web platform are organized around the application foundations for the Open Web Platform, a set of high-level components that application developers rely on to build their Web-based content and services.

The following application foundations are considered in this document: core web design and development, media and real-time communications, usability and accessibility, device interaction, application lifecycle, payment and services, performance & tuning, and security & privacy. In addition, it covers topics related to network integration.

The Web as an application development platform

In each category of features, a table summarizes for each feature:

which W3C specification defines the feature,
which W3C group is responsible of the said specification,
the stage of the specification in the W3C Recommendation track (see below),
the estimated stability of the feature, i.e. how little the author expects it to change, from an early draft that can still evolve a lot, to a finished document with only minor expected changes,
a link to the latest editors draft of the document, and a representation of the recent editing activity;
some qualitative indication on availability of implementations on mobile devices, based on data collected primarily from Can I Use… and mobile HTML5, completed with data from Mozilla developer network, QuirksMode, JWPalyer's state of HTML5 video, Chromium Dashboard, Internet Explorer Platform status, the Device APIs Working Group Implementation status as well as the author’s understanding of the mobile devices market (see also the code used to generate the support icons)
When available, a link to a relevant tutorial on WebPlatform Docs, and to relevant on-line training courses on W3DevCampus
a link to the test suite for the said feature, and when relevant, a github ribbon to access the underlying git repository.

W3C creates Web standards by progressing documents through its Recommendation track, with the following stages:

“Editors drafts” represent the current view of the editors of the specification but have no standing in terms of standardization.
“Working Drafts” (WD) are early milestones of the Working Group progress.
“Last Call Working Drafts” signal that the Working Group has determined that the specification fulfills its requirements and all the known issues have been resolved, and thus requests feedback from the larger community.
“Candidate Recommendations” (CR) trigger a call for implementations where implementors are invited to implement the specification and send feedback; Working Groups are expected to show the specification gets implemented by running test suites they have developed.
“Proposed Recommendations” (PR) manifests that the group has gathered sufficient implementation experience, and triggers the final review by W3C Members
“W3C Recommendations” (Rec) are stable and completed Web standards; these documents only get updated rarely, through the “Edited Recommendation” process, as a results from errata collected by Working Groups.

For groups that have adopted it, the 2014 update of the W3C Process simplifies a bit the progression by removing the Last Call stage — instead of a single global call for review addressed to the whole community, Working Groups are empowered with solicitting reviews from their various related communities as long as they can demonstrate sufficient wide review of the specification before requesting transition to Candidate Recommendation.

Prior to starting standardization, a Working Group needs to be chartered, based on input from W3C Members, often through the organization of a workshop, or after the reception of a W3C Member Submission.

W3C has set up Community Groups, a mechanism that allows anyone to do experimental work within the W3C infrastructure, under IPR rules that are compatible to transition the work to the W3C standardization process.

1. Core Web Design and Development

1.1 Graphics and Layout

SVG, Scalable Vector Graphics, provides an XML-based markup language to describe two-dimensions vector graphics. Since these graphics are described as a set of geometric shapes, they can be zoomed at the user request, which makes them well-suited to create graphics on mobile devices where screen space is limited. They can also be easily animated, enabling the creation of very advanced and slick user interfaces.

The integration of SVG in HTML5 opens up new possibilities, for instance applying advanced graphic filters (through SVG filters) to multimedia content, including videos. SVG 2.0 is set to facilitate that integration and complete the set of features in SVG.

In complement to the declarative approach provided by SVG, the <canvas> element added in HTML5 enables a 2D programmatic API that is well-suited for processing graphics in a less memory intensive way. That API not only allows rendering graphics, but can also be used to do image processing and analysis — HTML 5.1 adds the ability to do that processing in a separate Web Worker.

Both SVG and HTML can be styled using CSS (Cascading Style Sheets); in particular, CSS3 (the third level of the specification) is built as a collection of specifications set to offer a large number of new features that make it simple to create graphical effects, such as rounded corners, complex background images, shadow effects (CSS Backgrounds and Borders), rotated content (CSS Transforms, including with 3D effects).

Animations can be described declaratively via CSS Animations, and CSS Transitions.

Animations can also be managed via scripting through the API exposed in Web Animations; as they can be resource intensive, the possibility offered by the Timing control for script-based animations API to manage the rate of updates to animations can help keep them under control.

To ensure optimal performances when animating parts of an app, authors can make use of the CSS will-change property to let browsers compute the animation ahead of its occurrence.

CSS Flexbox allows to build complex layouts as required for interactive applications on small screens.

Fonts play also an important role in building appealing graphical interfaces, but mobile devices are in general distributed with only a limited set of fonts. WOFF 1.0 (Web Open Font Format) addresses that limitation by making it easy to use fonts that are automatically downloaded through style sheets, while keeping the size of the downloaded fonts limited to what is actually needed to render the interface. The upcoming WOFF 2.0 update to that format promises 25%-smaller download sizes; on mobile, a 35% reduction in the time needed to download and display these fonts has been measured.

Given the time required for downloading fonts over mobile networks, authors need to adapt their content to the progressive availability of fonts; CSS Font Loading gives the necessary events to developers to enable that adaptation.

Another important aspect in graphics-intensive applications (e.g. games) is the possibility to use the entire screen to display the said graphics; the work on a Fullscreen API to request and detect full screen display, previously co-developed by the Web Applications and CSS Working Groups, has now fully moved to the WHATWG.

Likewise, in these scenarios, it is often useful to be able to lock the orientation of the screen; the Screen Orientation API allows not only to detect orientation change, but also to lock the orientation in a specific state.

NB: a 3D graphic API for HTML5 canvas, called WebGL, has been developed outside of W3C, as part of the Khronos Group; this API has been built to be compatible with OpenGL ES, i.e. for embedded systems, and is intended to work on mobile devices.

Feature	Specification	Working Group	Stability	Latest editors draft	Current implementations	Test suite
2D Vector Graphics	Scalable Vector Graphics (SVG) 1.1 Specification	SVG	Finished	New version of SVG (SVG 2.0) in preparation	Widely deployed	High coverage
2D Vector Graphics	Scalable Vector Graphics (SVG) 2	SVG	Early draft	Last updated May 2015	N/A	N/A
2D Programmatic API	HTML Canvas 2D Context	HTML	Stable	Last updated December 2014	Widely deployed	Good coverage
2D Programmatic API	Canvas Proxy for Web Workers in HTML 5.1	HTML	Early draft	Last updated March 2015	None	None
Rounded Corners	CSS Backgrounds and Borders Module Level 3	CSS	Mostly finished	Last updated August 2014	Well deployed	Good coverage
Complex background images	CSS Backgrounds and Borders Module Level 3		Mostly finished	Last updated August 2014	Well deployed	Good coverage
Box shadow effects	CSS Backgrounds and Borders Module Level 3		Mostly finished	Last updated August 2014	Well deployed	Good coverage
2D Effects	CSS Transforms Module Level 1	SVG and CSS	Mostly stable	Last updated January 2015	Well deployed	Good coverage
3D Effects	CSS Transforms Module Level 1	SVG and CSS	Stabilizing	Last updated January 2015	Well deployed	Good coverage
Animations	CSS Animations	CSS	Early draft	Last updated May 2015	Well deployed	well started
	CSS Transitions	CSS	Early draft	Last updated May 2015	Well deployed	well started
	Web Animations 1.0	SVG and CSS	Early draft	Last updated May 2015	Limited	Well started
	Timing control for script-based animations	Web Performance	Stable	Last updated September 2014	Well deployed	Well started
	CSS Will Change Module Level 1	CSS	Early draft	Last updated February 2015	Growing deployment	N/A
Complex layouts	CSS Flexible Box Layout Module Level 1	CSS	Mostly finished	Last updated May 2015	Well deployed	Good coverage
Downloadable fonts	WOFF File Format 1.0	WebFonts	Finished	Finished	Good deployment	Good coverage
	WOFF File Format 2.0	WebFonts	Early draft	Last updated May 2015	Limited	N/A
	CSS Font Loading Module Level 3	CSS	Stabilizing	Last updated May 2015	Limited	N/A
Orientation Lock	The Screen Orientation API	Web Applications	Early draft	Last updated April 2015	Growing deployment	None

1.2. Device Adaptation

Mobile devices not only differ widely from traditional computers, but they also have a lot of variations among themselves, in term of screen size, resolution, type of keyboard, media recording capabilities, etc.

The Device Description Repository API is a unified server-side API that allows Web developers to retrieve data on the devices that are accessing their pages on a variety of device information database.

The Media Capture and Streams API exposes some specific information on capabilities of camera and microphones to make it possible to take advantage of the large variety of media capturing devices provided on mobile phones.

CSS Media Queries offer a mechanism that allows adapting the layout and behavior of a Web page based on some of the characteristics of the device, including the screen resolution — to which Media Queries Level 4 proposes to add the availability and type of a pointing device, the ability to hover over elements, and the ambient luminosity. It also lets developers the ability to define media queries that react to script-defined variables, making it easier to integrate these adaptation rules in the overall logic of the app.

CSS Device Adaptation defines a set of CSS directives to define the size on which this layout should be based, relatively to the size of the underlying device — specifying what has been implemented using the <meta name="viewport"> element so far.

The viewport-relative CSS units vw and vh let design layouts that adapt to the dimensions of the viewport, while CSS Mobile Text Size Adjustment lets text adapt to zoomed parts of a page.

The Responsive Images Community Group (RICG) developed an extension to HTML, known as the picture element, that allows authors define what image to load depending on device capabilities and/or other media features.

As a complementary approach, the srcset attribute, specified by the WHATWG and also published as an extension to HTML, let Web developers define the various device pixel ratios of an image, letting the browser pick the best choice for the pixel density of the screen. As of January 2014, there is general agreement amongst browser vendors to implement both picture and srcset.

SVG, which lets define images that can be scaled up and down without any loss of quality, is another critical tool to the development of Web applications that adapt to the resolution of the underlying device.

Feature	Specification	Working Group	Stability	Latest editors draft	Current implementations	Test suite
Device information	Device Description Repository Simple API	Device Description	finished	N/A	Limited	Good Coverage
Media Capture Capabilities	Source capabilities in Media Capture and Streams	Device APIs and Web Real-Time Communications	Stabilizing	Last updated May 2015	None	None
CSS-based adaptation	Media Queries	CSS	Finished	Finished	Widely deployed	Good coverage
	Media Queries Level 4		Early draft	Last updated May 2015	None	None
	CSS Device Adaptation		Early draft	Last updated April 2015	Limited	N/A
	viewport relative units in CSS Values and Units Module Level 3		Mostly finished	Last updated April 2015	Well deployed	Good coverage
	CSS Mobile Text Size Adjustment Module Level 1		Early draft	Last updated April 2013	Growing deployment	N/A
Responsive images	picture element in HTML 5.1	HTML	stabilizing	Last updated March 2015	Limited	Started
	srcset attribute in HTML 5.1	HTML	Stabilizing	Last updated March 2015	Growing deployment	Well started
	Scalable Vector Graphics (SVG) 1.1 Specification	SVG	Finished	New version of SVG (SVG 2.0) in preparation	Widely deployed	High coverage

1.3. Forms

The ability to build rich forms with HTML is the basis for user input in most Web-based applications. Due to their limited keyboards, text input on mobile devices remains a difficult task for most users; HTML5 address parts of this problem by offering new type of form controls that optimize the way users will enter data:

date and time entries can take advantage of a number of dedicated form controls (e.g. <input type="date">) where the user can use a native calendar control;
the <input type="email">, <input type="tel"> and <input type="url"> can be used to optimize the ways user enter these often-difficult to type data, e.g. through dedicated virtual keyboards, or by accessing on-device records for these data (from the address book, bookmarks, etc.);
the inputmode attribute (proposed in HTML 5.1) defines the type of textual input expected in a text entry;
the pattern attribute allows both to guide user input as well as to avoid server-side validation (which requires a network round-trip) or JavaScript-based validation (which takes up more resources);
the placeholder attribute allows to guide user input by inserting hints as to what type of content is expected in a text-entry control;
the <datalist> element allows creating free-text input controls coming with pre-defined values the user can select from; HTML 5.1 defines a mechanism for the autocomplete attribute to automatically fill input fields based on well-known data for the user.

Feature	Specification	Working Group	Stability	Latest editors draft	Current implementations	Test suite
Date and time entries	Data and Time input element in HTML5	HTML	Mostly stable	Last updated October 2014	Growing	Just started
Customized text entries (tel, email, url)	telephone, email and URL input element in HTML5		Stable	Last updated October 2014	Well deployed	Just started
Input modality	inputmode attribute in HTML 5.1		Early draft	Last updated March 2015	None	None
Input pattern	pattern attribute in HTML5		Stable	Last updated October 2014	Limited but growing	Just started
Input hint	placeholder attribute in HTML5		Stable	Last updated October 2014	Well deployed	Started
Autocomplete for text entries	datalist element in HTML5		Stable	Last updated October 2014	Growing	Started
Autocomplete for text entries	autocomplete attribute in HTML 5.1		Early draft	Last updated March 2015	Very limited	None

1.4 Data storage

A critical component of many applications is the ability to save state, export content, as well as integrate data from other files and services on the system.

For simple data storage, the Web Storage specification offers two basic mechanisms, localStorage and sessionStorage, that can preserve data respectively indefinitely, or on a browser-session basis.

For richer interactions, the Web platform provides the File Reader API makes it possible to load the content of a file.

Discussions have started on a new proposal for a sandboxed filesystem API.

Meanwhile, the HTML5 download attribute provides a simply mechanism to trigger a file download (rather than a page navigation), with the possibility of setting a user-friendly filename.

On top of this file-based access, the Indexed Database API (IndexedDB) defines a database of values and hierarchical objects that integrates naturally with JavaScript, and can be queried and updated very efficiently - a new second edition of the specification is under development. Note that the work around a client-side SQL-based database, which had been started in 2009, has been abandoned in favor of this new system.

As more and more data need to be stored by the browser (e.g. for offline usage), it becomes critical for developers to get reliable storage space, which the proposed Quota Management API will offer to Web applications.

Communication applications can benefit from integrating with their users’ existing data records; on mobile devices, the address book is a particularly useful source of information.

For Web apps outside of the browser, a purely programmatic approach is part of the System Applications Working Group, with work on a Contacts Manager API in progress.

In the browser, HTML 5.1 provides autocompleted fields for contacts information that would let browsers re-use data from addressbooks.

Some of this data need to be encrypted, the Web Cryptography API from the Web Cryptography Working Group exposes strong cryptography primitives to Web applications, and can be bound to pre-provisioned keys via the WebCrypto Key Discovery API.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Test suite
Simple data storage	Web Storage	Web Applications		Finished	Last updated May 2014	Well deployed	Complete
File operations	File API			Stabilizing	Last updated April 2015	Getting well deployed	Started
	FileSystem API		N/A	Early proposal	Last updated April 2015	N/A	None
	download attribute in HTML5	HTML		Stable	Last updated October 2014	Growing	None
Database query/update	Indexed Database API	Web Applications		Stable	Last updated May 2015	Well deployed	Good coverage
Database query/update	Web SQL Database		Retired	Abandoned	N/A	Somewhat deployed, but won’t be further deployed	N/A
Quota for storage	Quota Management API			Early work	Last updated April 2015	Very limited	None
Addressbook data	Contacts Manager API	System Applications		Early draft	Last updated April 2014	None	None
Addressbook data	autocomplete attribute in HTML 5.1	HTML		Early draft	Last updated March 2015	Very limited	None
Encrypted storage	Web Cryptography API	Web Cryptography		Stable	Last updated November 2014	Well deployed	Early start
Encrypted storage	WebCrypto Key Discovery	Web Cryptography		Early work	Last updated May 2014	None	None

2. Media and Real-Time Communications

HTML5 adds two tags that dramatically improve the integration of multimedia content on the Web: the <video> and <audio> tags. Respectively, these tags allow embedding video and audio content, and make it possible for Web developers to interact much more freely with that content than they would through plug-ins. They make multimedia content first-class citizens of the Web, the same way images have been for the past 20 years.

The playback content can be streamed, augmented and completed via Media Source Extensions that lets developers buffer and generate media content in JavaScript.

To cater for the needs of some content providers, a proposal to enable playback of protected content, Encrypted Media Extensions is an API that is under consideration in the HTML Working Group.

Mobile devices often expose shortcuts to handle the audio output of a main application (e.g. a music player) from a lock screen or the notification areas. The WHATWG Media Session specification proposes deeper integration with these features in Web applications.

Because mobile devices often come with a variety of configurable audio output (phone speaker, loudspeaker, headset, bluetooth speakers), the Audio Output Devices API let developers set on which ouput devices a given audio resource should play.

While the new HTML5 tags allow to play multimedia content, the HTML Media Capture defines a markup-based mechanism to access captured multimedia content using attached camera and microphones, a very common feature on mobile devices. The Web Real-Time Communications Working Group and the Device APIs Working Group are building together an API (getUserMedia) to directly manipulate streams from camera and microphones, as well as an API to record these streams into files, and another API to use access to cameras to take photos programatically.

Beyond capturing and recording, two additional APIs add multimedia manipulation capabilities to the Web platform. We have already mentioned the Canvas 2D Context API: it enables modifying images, which in turn opens up the possibility of video editing.

In a similar vein, the Audio Working Group is working on an API that that makes it possible to modify audio content, as well as analyze, modify and synthesize sounds, the Web Audio API.

The Network Service Discovery API offers to discover services on the local network (such as the ones offered via DLNA), enabling mobile Web applications to integrate seamlessly with these services.

An alternative proposal to the Network Service Discovery API has emerged: Named Web Sockets offers to provide well-known sockets to existing and approved local network services.

The Second Screen Presentation Working Group is building an an API to request display of content on an external screen, including through network-based protocols, forming the basis for second-screen scenarios.

The Web Real-Time Communications Working Group is the host of specifications for a wider set of communication opportunities:

Peer-to-peer connection across devices,
P2P Audio and video streams allowing for real-time communications between users.

The combination of all these features marks the starting point of the Web as a comprehensive platform for multimedia, both for consuming and producing. The rising interest around bridging the Web and TV worlds (manifested through the W3C Web and TV Interest Group) should strengthen that trend in the coming months. Mobile devices are expected to take a growing role in many users TV experience, providing a “second screen” experience, where users can find more information on or interact with a TV program they're watching via their mobile devices.

Likewise, the opportunity offered to deploy real-time communication services on the Web is another step towards the unification of the telecommunication and Web ecosystems.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Test suite
Video playback	video element in HTML5	HTML		Stable	Last updated October 2014	Good deployment	Well started
Audio playback	audio element in HTML5			Stable	Last updated October 2014	Good deployment	Started
Generation of media content	Media Source Extensions			Stable	Last updated April 2015	Well deployed	Well started
Protected content playback	Encrypted Media Extensions			Early draft	Last updated April 2015	Growing deployment	None
Media focus	Media Session	WHATWG	N/A	Early draft	Last updated May 2015	None	N/A
Audio output selection	Audio Output Devices API	Device APIs and Web Real-Time Communications		early draft	Last updated February 2015	None	None
Capturing audio/video	HTML Media Capture	Device APIs		Stable	Last updated October 2014	Growing deployment	Good coverage
	Media Capture and Streams	Device APIs and Web Real-Time Communications		Stabilizing	Last updated May 2015	Growing	started
	MediaStream Recording			Early draft	Last updated December 2014	Very limited	None
	Mediastream Image Capture			Early draft	Last updated January 2015	None	None
Image & Video analysis, modification	HTML Canvas 2D Context	HTML		Stable	Last updated December 2014	Widely deployed	Good coverage
Audio analysis, modification	Web Audio API	Audio		Starting to stabilize	Last updated May 2015	Good deployment	Started
Local network services	Network Service Discovery	Device APIs		Early draft, unsure future	Last updated February 2014	None	None
	Named Web Sockets	Device APIs	N/A	Early proposal	Last updated December 2014	None	None
	Presentation API	Second Screen Presentation		Early draft	Last updated May 2015	None	N/A
P2P connections and audio/video streams	WebRTC 1.0: Real-time Communication Between Browsers	Web Real-Time Communications		Early draft	Last updated March 2015	Growing	Very early start

3. Usability and Accessibility

An increasing share of mobile devices relies on touch-based interactions. While the traditional interactions recognized in the Web platform (keyboard, mouse input) can still be applied in this context, a more specific handling of touch-based input is a critical aspect of creating well-adapted user experiences, which Touch Events in the DOM (Document Object Model) enable. The work on that specification is now nearly finished.

Meanwhile, the Pointer Events Working Group has made good progress on an alternative approach to handle user input, Pointer Events, that allows to handle mouse, touch and pen events under a single model. It provides a complementary and more unified approach to the currently more widely deployed Touch Events.

In particular, the CSS property touch-action that lets filter gesture events on elements is gaining traction beyond implementations of Pointer Events.

As more and more content gets rendered as long scrollable lists, more and more logic is attached to scrolling events, and the quality of the user experience of these actions is highly dependent on their performances. The CSSOM View Module determines when scrolling events get fired, and let developers specify the type of scrolling behavior they want.

The proposed work on CSS Scroll Snap Points adds greater ability to control the behavior of panning and scrolling by defining points to which an app view would snap when the user moves through the page.

The CSS will-change property is also available to indicate to browsers that a given part of the page will be soon scrolled to and should be pre-rendered.

Many mobile devices use on-screen keyboards to let users type; the Input Method Editor (IME) API makes it possible to coordinate the interactions between that on-screen keyboard and Web applications, but the future of that API is under discussion given its relative lack of adoption.

Conversely, many mobile devices use haptic feedback (such as vibration) to create new form of interactions (e.g. in games); work on a vibration API in the Device APIs Working Group is making good progress.

But as the Web reaches new devices, and as devices gain new user interactions mechanisms, it also becomes important to allow Web developers to react to a more abstract set of user interactions: instead of having to work in terms of “click”, “key press”, or “touch event”, being able to react to an “undo” command, or a “next page” command independently of how the user instructed it to the device will prove beneficial to the development of device-independent Web applications. The IndieUI Events specification, developed by the Indie UI Working Group, aims at addressing this need.

Mobile devices follow their users everywhere, and many mobile users rely on them to remind them or notify them of events, such as messages: the Web Notifications specification enables that feature in the Web environment, while the Push API makes it possible for server-side notifications to alert the user, even if the browser is not running.

Mobile devices, and mobile phones in particular, are also in many cases well-suited to be used through voice-interactions; the Speech API Community Group is exploring the opportunity of starting standardization work around a JavaScript API that would make it possible for users to interact with a Web page through spoken commands.

Whether users are speaking commands to their apps or working with them through non-haptic interactions, they risk seeing the screens turned off automatically by their devices screensaver. An early proposal for a Wake Lock API would let developers signal the needs to keep the screen up in these circumstances.

The hardware constraints of mobile devices, and their different usage context can make mobile users experience similar barriers to people with disabilities. These similarities in barriers mean that similar solutions can be used to cater for them, making a Web site accessible both for people with disabilities and mobile devices a natural goal (as detailed in Relationship between Mobile Web Best Practices and WCAG).

The WCAG and UAWG Working Group provide guidance on mobile accessibility in how Web Content Accessibility Guidelines (WCAG) and other WAI guidelines apply to mobile — that is, making websites and applications more accessible to people with disabilities when they are using mobile phones and a broad range of other devices.

WAI-ARIA provides semantic information on widgets, structures and behaviors hooks to make Web applications more accessible, including on mobile devices.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Test suite
Touch-based interactions	Touch Events	Web Events		Finished	Last updated July 2014	Largely deployed	Complete
	Pointer Events	Pointer Events		Stable	Last updated December 2014	Limited deployment	Well started
	touch-action property in Pointer Events	Pointer Events		Stable	Last updated December 2014	Growing	Good coverage
Smooth scrolling	smooth scrolling in CSSOM View Module	CSS		Still changing	Last updated December 2014	None	N/A
	CSS Scroll Snap Points Module Level 1			Early draft	Last updated April 2015	Experimental	None
	CSS Will Change Module Level 1			Early draft	Last updated February 2015	Growing deployment	N/A
On-screen keyboard interactions	Input Method Editor API	Web Applications		Uncertainty about future	Last updated April 2015	Very limited	N/A
Vibration	Vibration API	Device APIs		Finished	Last updated November 2014	Growing	Good coverage
Intent-based events	IndieUI: Events 1.0	Independent User Interface (Indie UI)		Early draft	Last updated June 2014	None	None
Notification	Web Notifications	Web Notification		Stable	Last updated January 2015	Growing deployment	Well started
Notification	Push API	Web Applications		Early draft, now with Service Workers	Last updated May 2015	Limited	N/A
Speech-based interactions	Web Speech API	Speech API Community Group	N/A	N/A	Last updated January 2013	Limited	N/A
Screen wake	Wake Lock API	Device APIs		Just started	Last updated February 2015	None	N/A
Accessibility	Relationship between Mobile Web Best Practices (MWBP) and Web Content Accessibility Guidelines (WCAG)	Mobile Web Best Practices and Education and Outreach	NOTE	Finished	N/A	N/A	N/A
	Mobile Accessibility: How WCAG 2.0 and Other W3C/WAI Guidelines Apply to Mobile	Web Content Accessibility Guidelines and User Agent Accessibility Guidelines		Early draft	Last updated April 2015	N/A	N/A
	Accessible Rich Internet Applications (WAI-ARIA) 1.0	Protocols and Formats		Stable	Finished	Well deployed	Good coverage

4. Device interaction

Mobile devices are packed with sensors, making them a great bridge between the real and virtual worlds: GPS, accelerometer, ambient light detector, microphone, camera, thermometer, etc.

To take full advantage of these sensors in mobile Web applications, Web developers need to be provided with hooks to interact with them.

The Geolocation API provides a common interface for locating the device, independently of the underlying technology (GPS, WIFI networks identification, triangulation in cellular networks, etc.).

Work towards a new geofencing API (i.e. an API to detect when a device enters a given geographical area) has started.

Web applications can also now access orientation and acceleration data via the DeviceOrientation Event Specification.

A number of APIs for other sensors are under development: the Battery Status API, the Proximity Events API, the Ambient Light Events API or the proposed Ambient Humidity Events API. The Device APIs Working Group has started an effort to propose a unification pattern for these various sensors.

As already mentioned in the section on multimedia, there is ongoing work on APIs to open up access to camera and microphone streams.

The NFC Working Group had been chartered to develop APIs for accessing from Near-Field Communications systems to Web runtimes, but outside the traditional Web security model; as the need and requirements to bring NFC interactions under that model have become clearer, the existing NFC Working Group has been closed, and work on browser-compatible NFC API has started in the Web NFC Community Group.

A more global access to sensors and hardware (including USB and bluetooth) is in scope for the System Applications Working Group. A Web Bluetooth Community Group was started to develop a Bluetooth API for browsers with a particular goal of supporting Bluetooth Low Energy devices.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Test suite
Geolocation	Geolocation API Specification	Geolocation		Finished	Last updated July 2014	Widely deployed	Good coverage
Geolocation	Geofencing API			Just started	Last updated May 2015	None	None
Motion sensors	DeviceOrientation Event Specification			Stabilizing, but with planned updates	Last updated August 2014	Well deployed	Started
Battery Status	Battery Status API	Device APIs		Stable	Last updated November 2014	Limited, but growing	Good coverage
Proximity sensors	Proximity Events			Likely to evolve substantially	Last updated April 2014	Very limited	Started
Ambient Light sensor	Ambient Light Events			Likely to evolve significantly	Last updated February 2015	Very limited	Started
Humidity sensor	Ambient Humidity Events		N/A	Unofficial draft	Last updated October 2013	None	N/A
Camera & Microphone streams	Media Capture and Streams	Device APIs and Web Real-Time Communications		Stabilizing	Last updated May 2015	Growing	started
NFC	Web NFC API	Web NFC Community Group	Not on standards track	Early draft	Last updated May 2015	None	N/A
Bluetooth	Web Bluetooth	Web Bluetooth Community Group	Not on standards track	Early draft	Last updated May 2015	None	N/A

5. Network Integration

Network connectivity represents a major asset for mobile devices: the Web is an immense store of content, as well as an almost endless source of processing power, overcoming two of the limitations of mobile devices.

The Web platform is growing a number of APIs that facilitate establishing network connectivity in different contexts.

XMLHttpRequest (the basis for Ajax development) is a widely deployed API to load content from Web servers using the HTTP and HTTPs protocol: the W3C specification (formerly known as XMLHttpRequest Level 2) completes the existing deployed API with the ability to make requests on servers in a different domain, programmatic feedback on the progress of the network operations, and more efficient handling of binary content. The WHATWG fetch API provides a more powerful Promise-based alternative.

The Beacon API aims at letting developers queue unsupervised HTTP requests, leaving it to the browser to execute them when appropriate, opening the door for better network optimizations.

Early work on a Web Background Synchronization API would provide a robust Service Worker-based mechanism to enable Web applications to download and upload content in the background, even in the absence of a running browser.

By default, browsers do not allow to make request across different domains (or more specifically, across different origins, a combination of the protocol, domain and port) from a single Web page; this rule protects the user from having a Web site abusing their credentials and stealing their data on another Web site. Sites can opt-out of that rule by making use of the Cross-Origin Resource Sharing mechanism, opening up much wider cooperation across Web applications and services.

XMLHttpRequest is useful for client-initiated network requests, but mobile devices with their limited network capabilities and the cost that network requests induce on their battery (and sometimes on their users bill) can often make better use of server-initiated requests. The Server-Sent Events API allows triggering DOM events based on push notifications (via HTTP and other protocols.)

Early work on a Push API would allow Web applications to receive server-sent messages whether or not the said Web app is active in a browser window. An IETF Working Group charter is under discussion to standardize the protocol aspects of the mechanism.

The WebSocket API, built on top of the IETF WebSocket protocol, offers a bidirectional, more flexible, and less resource intensive network connectivity than XMLHttpRequest.

The work on Web Real-Time Communications will also provide direct peer-to-peer data connections between browsers with real-time characteristics, opening the way to collaborative multi-devices Web applications.

Of course, an important part of using network connectivity relies on being able to determine if such connectivity exists, and the type of network available. The HTML5 onLine DOM flag (and its associated change event, ononline) signals when network connectivity is available to the Web environment.

The network-information API, which was supposed to address discovery of the network characteristics, has been abandoned for the time being due to lack of clear supporting use cases.

The Resource Timing API offers to measure precisely the impact of the network on the time needed to load various resources, offering another approach to adapt a Web app to its network environment.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Test suite
HTTP(s) network API	XMLHttpRequest Level 1	Web Applications		stabilizing	Last updated May 2014	Well deployed	Good coverage
	Beacon	Web Performance		Stabilizing	Last updated April 2015	Limited but growing	N/A
	Web Background Synchronization	Web Applications	N/A	Early draft	Last updated April 2015	None	None
Cross-domain requests	Cross-Origin Resource Sharing	Web Applications and Web Application Security		Stable	Finished	Well-deployed	Well started
Server-pushed requests	Server-Sent Events	Web Applications		Stable	Last updated May 2014	Getting well-deployed	Good coverage
Server-pushed requests	Push API			Early draft, now with Service Workers	Last updated May 2015	Limited	N/A
Bidirectional connections	The WebSocket API			Stable	Last updated June 2014	Good deployment	Good coverage
P2P data connections	WebRTC 1.0: Real-time Communication Between Browsers	Web Real-Time Communications		Early draft	Last updated March 2015	Growing	Very early start
on-line state	onLine state in HTML5	HTML		Stable	Last updated October 2014	Limited	Well started
Network characteristics	The Network Information API	Device APIs	Retired	Abandoned for now, but might be restarted	Last updated November 2014	Limited	None
Network characteristics	Resource Timing	Web Performance		Stable	Last updated May 2015	Growing	Well started

6. Application Lifecycle

An important aspect of the user experience of applications is linked to how the user perceives the said application is available permanently (even when off-line, which is particularly important on mobile devices), as well as its ability to get started based on external notifications.

These notions are part of the overall application lifecycle: how applications get installed, shown to the user in applications list, started, stopped, woken up from remote notifications, synced up when the device goes on-line.

These various capabilities are brought the Web platform through different mechanisms.

Although the notion of installed Web applications is still not well-defined, there are several components to the notion of installation that are under development.

Packaging on the Web describes a Web-adapted format to make Web content available in a singe file for ease of download, sharing or archiving.

Whether packaged or not, users rely on a variety of metadata (name, icons) to identify the apps they want to use among their list of regularly used applications. The JSON-based manifest format lets developers group all these metadata in a single JSON file.

HTML5’s ApplicationCache enables access to Web applications off-line through the definition of a manifest of files that the browser is expected to keep in its cache.

While relatively well deployed, the current approach has shown some strong limitations in terms of how much developers can control what gets cached when. The Web Applications Working Group has thus been developing a more powerful approach, ServiceWorker.

Not only does Service Worker enables Web applications to work seamlessly off-line or in poor network conditions, it also creates a model for Web applications to operate when they have not been opened in a browser window, or even if the browser itself is not running.

That ability opens the door for Web applications that run in the background and can react to remotely triggered events.

The Task Scheduler API makes it possible to trigger a task at a specified time via the Web app service worker.

Similarly, the new geofencing API enables to wake up a Web app when a device enters a specified geographical area.

The Push API enables Web applications to subscribe to remote notifications that, upon reception, wake them up. Native applications have long enjoyed the benefits of greater user engagement that these notifications bring, and soon Web applications will share that ability.

Likewise, the Web Background Synchronization specification will enable Web applications to keep their user data up to date seamlessly, by running network operations in the background.

The Page Visibility specification lets developers detect when their application is in the foreground, and thus adapt their operations and resource consumption accordingly.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Test suite
Packaging	Packaging on the Web	TAG and Web Applications		Early draft	Last updated February 2015	None	N/A
Packaging	Manifest for a web application	Web Applications		Early draft	Last updated May 2015	Limited	N/A
Offline Web Apps	ApplicationCache in HTML5	HTML		Stable (but Service Workers will be the preferred approach when available)	Last updated October 2014	Well deployed	None
Offline Web Apps	Service Workers	Web Applications		Early draft	Last updated May 2015	None	Well started
Scheduled tasks	Task Scheduler API Specification	System Applications		Early draft	Last updated October 2014	None	None
Geofencing	Geofencing API	Geolocation		Just started	Last updated May 2015	None	None
Remote Notifications	Push API	Web Applications		Early draft, now with Service Workers	Last updated May 2015	Limited	N/A
Background Sync	Web Background Synchronization	Web Applications	N/A	Early draft	Last updated April 2015	None	None
Foreground detection	Page Visibility	Web Performance		Finished	Finished	Well deployed	Good coverage

7. Payment and Services

Native mobile application stores have made it much easier for developers to monetize some of their applications, either by selling the application itself to users, or by providing in-app purchases.

While Web applications can use well-known on-line payment solutions, these solutions have so far proved much harder to use on mobile devices.

In March 2014, W3C organized a workshop on Web payments to identify ways in which standards could help make that payment experience much simpler, in particular on mobile devices. In Octobober 2014, W3C chartered the Web Payment Interest Group to drive work in this space, and that group released its sense of priority use cases for Web payments which should lead to new standardization work in the upcoming few months.

Meanwhile, HTML5.1 provides specific help for autocomplete of credit card details, making it easier to pay via credit cards once these details have been entered once.

Feature	Specification	Working Group	Maturity	Stability	Latest editors draft	Current implementations	Developers doc	Test suite
Integrated payment	Credit card details autocomplete in HTML 5.1	HTML		Early draft	Last updated March 2015	Very limited		None

8. Performance & Tuning

Due to their limited CPU, and more importantly to their limited battery, mobile devices require a lot of attention in terms of performance.

The work started by the Web Performance Working Group on Navigation Timing, Resource Timing, Performance Timeline and User Timing, gives tools to Web developers for optimizing their Web applications. The work on the Frame Timing API aims at providing detailed information on the frame-per-second obtained when an application is running on the user device.

The Resource Hints specification let developers indicate what resources should be downloaded when the browser can afford it.

The proposed work on Efficient Script Yielding offers the opportunity to Web developers to use more efficiently asynchronous programming, but has so far gained very limited traction.

The API to determine whether a Web page is being displayed (Page Visibility API) can also be used to adapt the usage of resources to the need of the Web application, for instance by reducing network activity when the page is minimized. Likewise, the Timing control for script-based animations API can help reduce the usage of resources needed for playing animations.

Beyond optimization of resources, the perceived reactivity of an application is also a critical aspect of the mobile user experience. The thread-like mechanism made possible via Web Workers allows keeping the user interface responsive by offloading the most resource-intensive operations into a background process.

The battery API allows adjusting the use of resources to the current level of power available in the battery of a mobile device.

The Mobile Web Application Best Practices provide general advice on how to build Web applications that work well on mobile devices, taking into account in particular the needs for optimization. The opportunity to update these best practices is under discussion in the Web and Mobile Interest Group.

Feature	Specification	Working Group	Stability	Latest editors draft	Current implementations	Test suite
Timing hooks	Navigation Timing	Web Performance	Finished	Finished	Well deployed	Good coverage
	Resource Timing		Stable	Last updated May 2015	Growing	Well started
	Performance Timeline		Finished	Finished	Limited	Started
	User Timing		Finished	Finished	Growing	Well started
	Frame Timing		Early draft	Last updated April 2015	None	None
Network prioritization	Resource Hints		Early draft	Last updated April 2015	None?	None
Priority handling	Efficient Script Yielding		Early draft	Last updated April 2014	Very limited	None
Page Visibility detection	Page Visibility		Finished	Finished	Well deployed	Good coverage
Animation optimization	Timing control for script-based animations		Stable	Last updated September 2014	Well deployed	Well started
Threading	Web Workers	Web Applications	Stable	Last updated May 2014	Well deployed	Good coverage
Battery Status	Battery Status API	Device APIs	Stable	Last updated November 2014	Limited, but growing	Good coverage
Optimization Best Practices	Mobile Web Application Best Practices	Mobile Web Best Practices	Finished	N/A	N/A	N/A

9. Security & Privacy

Mobile devices follow their users everywhere, and hold some of their most private or confidential data (contacts, pictures, calendar, etc.) As a result, it is critical for users to be able to rely on their phones to keep that data safe from attackers.

W3C specifications are reviewed for their security and privacy impact as part of their progress through the Recommendation track; the Privacy Interest Group and the Web Security Interest Group in particular are coordinating reviews on their respective fields.

Many sensitive APIs are gated by a request for user consent; while these requests give control to the user, they can be sometimes hard to integrate in the overall user experience without visibility on which permission has been granted or denied. The Permissions API aims at fixing this.

But beyond these cross-technology considerations, a number of ongoing work items address needs for additional protection.

The first line of defense for users, and the unit of isolation for Web apps is the same-origin policy that roughly limits what a Web application can access to content and data hosted on the same origin, i.e. the combination of URL scheme, domain name and port.

For legacy reasons, this policy is not as stringent on some parts of the Web platform, exposing users to greater attack surface via cross-site scripting or cross-site request forgery. To enable Web application authors to reduce the attack surface beyond what legacy requires, the Content Security Policy (level 2) offers hooks that severely limits damages that an attacker could hope to achieve.

To further strengthen the integrity of their applications, Web developers can make use of the proposed Subresource integrity mechanism, that makes it possible to block man-in-the-middle attacks or compromised third-parties providers.

In applications that aggregate content from multiple (possibly untrusted) sources, the HTML5 iframe sandbox makes it possible to restrict what kind of interactions third-party embedded content can make use of.

As described earlier, the Web Cryptography API provides the necessary tools to encrypt data for storage and transmission from within Web applications, with access pre-provisioned keys via the WebCrypto Key Discovery API.

For users that wish to indicate their preferences not to be tracked across Web applications and sites, the Tracking Preference Expression (also known as Do No Track) enables browsers to communicate explicitly their wish to content providers, and to determine whether a given content provider asserts fulfilling that wish.

To facilitate the authentication of users to on-line services, the Web Application Security Working Group is proposing a credential management API that lets developers interact more seamless with user-agent-managed credentials.

Feature	Specification	Working Group	Stability	Latest editors draft	Current implementations	Test suite
Permission management	The Permissions API	Web Application Security	Early draft	Last updated April 2015	None	N/A
Strengthened security	Content Security Policy Level 2		Stable	Last updated April 2015	Well-deployed	Well started
	Subresource Integrity		Just started	Last updated May 2015	None	None
	Sandboxed iframe in HTML5	HTML	Stable	Last updated October 2014	Widely deployed	None
Encrypted storage	Web Cryptography API	Web Cryptography	Stable	Last updated November 2014	Well deployed	Early start
Encrypted storage	WebCrypto Key Discovery	Web Cryptography	Early work	Last updated May 2014	None	None
Tracking protection	Tracking Preference Expression (DNT)	Tracking Protection	Stabilizing	Last updated April 2015	Good deployment	None
Identity management	Credential Management Level 1	Web Application Security	Early draft	Last updated May 2015	None	N/A

Acknowledgments

Thanks to Art Barstow, Anssi Kostiainen, Jo Rabin, J. Manrique López, Mounir Lamouri, Marcos Caceres, François Daoust and Ronan Cremin for their contributions to this document.

This document is produced through the HTML5Apps project, funded by the European Union through the Seventh Framework Programme (FP7/2013-2015) under grant agreement n°611327 - HTML5 Apps.