Alt (or alternative) text
The required text providing a succinct description of an image. When writing alt text, consider what you would say about the image if you were reading aloud your post over the phone.
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Assistive (or adaptive) technology (AT)
Software or hardware created or modified to enable people with disabilities to use computers.
Examples of assistive technologies that may be used while surfing the web include the following:
  • Alternative keyboards and switches/pointing devices: A variety of input methods used in place of the standard keyboard and mouse. Used by individuals with limited hand function or severe mobility impairments.
  • Refreshable Braille display: Hardware in which pins raise and lower to display Braille, a tactile system using raised dots to represent letters and numbers. Used by individuals with visual impairments or who are deaf-blind.
  • Scanning software: Software that highlights selection choices (e.g., letters, menu items, links, phrases) one at a time. User selects desired item by hitting a switch when the desired item is highlighted or announced. Used by individuals with physical or cognitive disabilities.
  • Screen magnifier: Software that magnifies a portion of the screen for easier viewing. Used by individuals with low vision.
  • Screen reader: Software that interprets what is displayed on screen and directs it to either speech synthesis for audio output or a refreshable Braille display for tactile output. Used by individuals who are blind or have reading disabilities.
  • Speech recognition software: Software that allows input using voice; for example, Dragon Naturally Speaking. Used by individuals with limited or no hand function, or with learning disabilities.
Auditory description
A verbal description providing information about actions, body language, graphics, and scene changes in a video. Must be synchronized with the auditory track of the video, usually during natural pauses in the auditory track. Used by people who are blind or have low vision; may also be used as a low-bandwidth equivalent on the web.
Text synchronized with the spoken word and sounds in a video. Captions are typically superimposed or overlayed along the bottom of the video. 
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Image Title
An optional bit of text providing additional information or a caption for the image. In most browsers, the title appears as a tool tip when hovering the mouse over the image.
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A text version of the video that includes the dialogue and additional information about the setting, actions and such.
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