A screen reader is a form of
assistive technology (
AT) that renders text and image content as speech or braille output. Screen readers are essential to people who are
blind,
and are useful to people who are
visually impaired,
illiterate, or have a
learning disability.
Screen readers are
software applications that attempt to convey what people with normal eyesight see on a
display to their users via non-visual means, like
text-to-speech
Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware products. A text-to-speech (TTS) system converts normal langu ...
, sound icons, or a
braille device.
They do this by applying a wide variety of techniques that include, for example, interacting with dedicated
accessibility APIs, using various
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
features (like
inter-process communication and querying
user interface properties), and employing
hooking techniques.
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
operating systems have included the
Microsoft Narrator screen reader since
Windows 2000
Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was released to manufacturing on December 15, 1999, and was offici ...
, though separate products such as
Freedom Scientific
Freedom Scientific is a company that makes accessibility products for computer users with low vision and blindness. The software they create enables screen magnification, screen reading, and use of refreshable braille displays with modern compu ...
's commercially available
JAWS
Jaws or Jaw may refer to:
Anatomy
* Jaw, an opposable articulated structure at the entrance of the mouth
** Mandible, the lower jaw
Arts, entertainment, and media
* Jaws (James Bond), a character in ''The Spy Who Loved Me'' and ''Moonraker''
* ...
screen reader and
ZoomText screen magnifier and the
free and open source
Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the source ...
screen reader
NVDA by NV Access are more popular for that operating system.
Apple Inc.'s
macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...
,
iOS, and
tvOS include
VoiceOver as a built-in screen reader, while
Google
Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
's
Android provides the
Talkback screen reader and its
ChromeOS can use ChromeVox. Similarly, Android-based devices from Amazon provide the VoiceView screen reader. There are also free and open source screen readers for
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...
and
Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
systems, such as Speakup and
Orca
The orca or killer whale (''Orcinus orca'') is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. It is the only extant species in the genus '' Orcinus'' and is recognizable by its black-and-white ...
.
Types
Command-line (text)
In early
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s, such as
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few o ...
, which employed
command-line interface
A command-line interpreter or command-line processor uses a command-line interface (CLI) to receive commands from a user in the form of lines of text. This provides a means of setting parameters for the environment, invoking executables and pro ...
s (
CLIs), the screen display consisted of
characters mapping directly to a
screen buffer in
memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remember ...
and a
cursor position. Input was by keyboard. All this information could therefore be obtained from the system either by
hooking the flow of information around the system and reading the screen buffer or by using a standard hardware output socket and communicating the results to the user.
In the 1980s, the Research Centre for the Education of the Visually Handicapped (
RCEVH) at the
University of Birmingham developed a Screen Reader for the
BBC Micro and NEC Portable.
Graphical
Off-screen models
With the arrival of
graphical user interface
The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, ins ...
s (
GUIs), the situation became more complicated. A
GUI has characters and graphics drawn on the screen at particular positions, and therefore there is no purely textual representation of the graphical contents of the display. Screen readers were therefore forced to employ new low-level techniques, gathering messages from the
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
and using these to build up an "off-screen model", a representation of the display in which the required text content is stored.
For example, the operating system might send messages to draw a command button and its caption. These messages are intercepted and used to construct the off-screen model. The user can switch between controls (such as buttons) available on the screen and the captions and control contents will be read aloud and/or shown on a
refreshable braille display
A refreshable braille display or braille terminal is an electro-mechanical device for displaying braille characters, usually by means of round-tipped pins raised through holes in a flat surface. Visually impaired computer users who cannot use a s ...
.
Screen readers can also communicate information on menus, controls, and other visual constructs to permit blind users to interact with these constructs. However, maintaining an off-screen model is a significant technical challenge; hooking the low-level messages and maintaining an accurate model are both difficult tasks.
Accessibility APIs
Operating system and application designers have attempted to address these problems by providing ways for screen readers to access the display contents without having to maintain an off-screen model. These involve the provision of alternative and accessible representations of what is being displayed on the screen accessed through an
API. Existing
APIs include:
* Android Accessibility Framework
* Apple Accessibility
API
*
AT-SPI
Assistive Technology Service Provider Interface (AT-SPI) is a platform-neutral framework for providing bi-directional communication between assistive technologies (AT) and applications. It is the ''de facto'' standard for providing accessibility ...
*
IAccessible2
*
Microsoft Active Accessibility (
MSAA)
*
Microsoft UI Automation
*
Java Access Bridge
The Java Access Bridge (JAB) exposes accessibility information about Java components to screen readers and other assistive technologies running on the Windows platform.
Prior to Java SE Version 7 Update 6, the Java Access Bridge needed to be inst ...
Screen readers can query the operating system or application for what is currently being displayed and receive updates when the display changes. For example, a screen reader can be told that the current focus is on a button and the button caption to be communicated to the user. This approach is considerably easier for the developers of screen readers, but fails when applications do not comply with the accessibility
API: for example,
Microsoft Word does not comply with the
MSAA API, so screen readers must still maintain an off-screen model for Word or find another way to access its contents. One approach is to use available operating system messages and application object models to supplement accessibility
APIs.
Screen readers can be assumed to be able to access all display content that is not intrinsically inaccessible. Web browsers, word processors, icons and windows and email programs are just some of the applications used successfully by screen reader users. However, according to some users, using a screen reader is considerably more difficult than using a GUI, and many applications have specific problems resulting from the nature of the application (e.g. animations) or failure to comply with accessibility standards for the platform (e.g. Microsoft Word and Active Accessibility).
Self-voicing programs and applications
Some programs and applications have voicing technology built in alongside their primary functionality. These programs are termed
self-voicing A self-voicing application is an application that provides an aural interface without requiring a separate screen reader. Self-voicing applications can be an important form of assistive technology, useful to those who have difficulty reading or see ...
and can be a form of
assistive technology if they are designed to remove the need to use a screen reader.
Cloud-based
Some telephone services allow users to interact with the internet remotely. For example, TeleTender can read web pages over the phone and does not require special programs or devices on the user side.
Virtual assistants can sometimes read out written documents (textual web content,
PDF documents, e-mails etc.) The best-known examples are Apple's
Siri,
Google Assistant, and
Amazon Alexa
Amazon Alexa, also known simply as Alexa, is a virtual assistant technology largely based on a Polish speech synthesiser named Ivona, bought by Amazon in 2013. It was first used in the Amazon Echo smart speaker and the Echo Dot, Echo Studio ...
.
Web-based
A relatively new development in the field is web-based applications like Spoken-Web that act as web portals, managing content like news updates, weather, science and business articles for visually-impaired or blind computer users. Other examples are ReadSpeaker or
BrowseAloud BrowseAloud is assistive technology software that adds text-to-speech functionality to websites. It is designed by Texthelp Ltd, a Northern Ireland based company that specialises in the design of assistive technology. BrowseAloud adds speech and rea ...
that add
text-to-speech
Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or hardware products. A text-to-speech (TTS) system converts normal langu ...
functionality to web content. The primary audience for such applications is those who have difficulty reading because of learning disabilities or language barriers. Although functionality remains limited compared to equivalent desktop applications, the major benefit is to increase the accessibility of said websites when viewed on public machines where users do not have permission to install custom software, giving people greater "freedom to roam".
This functionality depends on the quality of the software but also on a logical structure of the text. Use of headings, punctuation, presence of alternate attributes for images, etc. is crucial for a good vocalization. Also a web site may have a nice look because of the use of appropriate two dimensional positioning with CSS but its standard linearization, for example, by suppressing any CSS and Javascript in the browser may not be comprehensible.
Customization
Most screen readers allow the user to select whether most
punctuation
Punctuation (or sometimes interpunction) is the use of spacing, conventional signs (called punctuation marks), and certain typographical devices as aids to the understanding and correct reading of written text, whether read silently or aloud. A ...
is announced or silently ignored. Some screen readers can be tailored to a particular application through
scripting. One advantage of scripting is that it allows customizations to be shared among users, increasing accessibility for all.
JAWS
Jaws or Jaw may refer to:
Anatomy
* Jaw, an opposable articulated structure at the entrance of the mouth
** Mandible, the lower jaw
Arts, entertainment, and media
* Jaws (James Bond), a character in ''The Spy Who Loved Me'' and ''Moonraker''
* ...
enjoys an active script-sharing community, for example.
Verbosity
Verbosity is a feature of screen reading software that supports vision-impaired computer users. Speech verbosity controls enable users to choose how much speech feedback they wish to hear. Specifically, verbosity settings allow users to construct a mental model of web pages displayed on their computer screen. Based on verbosity settings, a screen-reading program informs users of certain formatting changes, such as when a frame or table begins and ends, where graphics have been inserted into the text, or when a list appears in the document. The verbosity settings can also control the level of descriptiveness of elements, such as lists, tables, and regions. For example,
JAWS
Jaws or Jaw may refer to:
Anatomy
* Jaw, an opposable articulated structure at the entrance of the mouth
** Mandible, the lower jaw
Arts, entertainment, and media
* Jaws (James Bond), a character in ''The Spy Who Loved Me'' and ''Moonraker''
* ...
provides low, medium, and high web verbosity preset levels. The high web verbosity level provides more detail about the contents of a webpage.
Language
Some screen readers can read text in more than one
language
Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...
, provided that the language of the material is encoded in its
metadata.
Some screen reading programs also include language verbosity, which automatically detects verbosity settings related to speech output language. For example, if a user navigated to a website based in the United Kingdom, the text would be read with
an English accent.
See also
*
List of screen readers
*
Screen magnifier
*
Speech processing
*
Speech recognition
Speech recognition is an interdisciplinary subfield of computer science and computational linguistics that develops methodologies and technologies that enable the recognition and translation of spoken language into text by computers with the ...
*
Speech synthesis
*
Vinux
*
VoiceOver
References
External links
Fangs screen reader emulatorn open-source Mozilla
Firefox extension
This is a list of WebExtensions that are recommended by Mozilla.
Mozilla software
Firefox
Firefox compatibility
Thunderbird
Notes
References
External links
Official add-ons site for Mozilla products
{{DEFAULTSORT:List Of Firefox ...
that simulates how a web page would look in
JAWS
Jaws or Jaw may refer to:
Anatomy
* Jaw, an opposable articulated structure at the entrance of the mouth
** Mandible, the lower jaw
Arts, entertainment, and media
* Jaws (James Bond), a character in ''The Spy Who Loved Me'' and ''Moonraker''
* ...
{{authority control
Assistive technology