Accessibility Guide for deafblind
Ensures that components with the label role="img"
have an alternate text.
Even if an image merely contains text, screen readers are unable to convert it into words that the user can hear. As a result, alternative language for images must be brief, descriptive, and easily understandable so that screen reader users may understand the image’s contents and intended application.
Without an accessible text alternative that screen readers can translate into sound or braille, all visual information, including images, is utterly useless if you can’t see. Accessible alternate text is also necessary to variable degrees for people with low vision or color blindness problems.
If an image does not have a text alternative that is accessible, screen readers cannot translate the information in the image to voice or braille.
What this Accessibility Rule Checks
Elements with the property value role="img"
must additionally have markup that specifies accessible alternative text for the image.
For screen reader users to efficiently navigate tables, the scope
element must be utilized correctly on tables in accordance with either HTML4 or HTML5 specifications.
If utilized properly, the scope
feature greatly simplifies table navigation for screen reader users. When misused, scope
can make table navigation far more difficult and ineffective.
The assumption made by a screen reader is that a table has a header that identifies a scope. Having an accurate header makes viewing a table for those who use screen readers far more accessible and effective due to the way the devices work.
What this Accessibility Rule Checks
Ensures that tables are correctly using the scope
attribute.
Elements with scrollable content must be keyboard-accessible.
This rule searches scrollable content for elements that can be focused to enable keyboard navigation. When the focus shifts to an element within a scrollable region, keyboard navigation shouldn’t stop working.
What this Accessibility Rule Checks
Check to see if the scrollable area has keyboard access.
An image map that is server-side rather than client-side is present in the page.
Server-side image maps can’t be used with a keyboard since mouse clicks are needed to access the links they contain, rendering them unavailable to users who only use keyboards.
The server-side software used to process the image map receives the locations of the mouse click from server side image maps. They are not keyboard accessible since they rely on mouse clicks, although client-side image mappings are. Additionally, unlike the regions
of a client-side picture map, actionable areas of a server-side image map cannot be provided with text alternatives.
What this Accessibility Rule Checks
Makes sure that server-side image maps are not used.
In order to save viewers time, the website must contain a link at the top before the navigation that directs them directly to the page’s core content.
As it appears in the HTML file, screen readers read the text sequentially.
This has the effect of reading out to users of assistive technology the content at the top of the page, which normally includes the full navigation, before they can access any of the primary content. When a user is primarily interested in the main material, it might be time-consuming to listen to or navigate through all of the text at the top of the page because it is frequently very long.
Users who are blind, have low eyesight, or only use the mouse will benefit from an HTML website having a skip link.
What this Accessibility Rule Checks
Ensures that programmers adhere to the best practice of placing a skip link as the page’s very first link.
Ensures that SVG elements with the roles img
, graphics-document
or graphics-symbol
have a text alternative that is accessible.
In order to make information provided by non-text material (including SVG graphics) accessible, Success Criterion 1.1.1 requires the usage of a text alternative. Because they can be portrayed through any sensory modality (for example, visual, auditory, or tactile) to suit the user’s needs, text alternatives are a fundamental method of making information accessible. By including text alternatives, a wider range of user agents can present the content in different ways.
For instance, a person who is blind can request that the text equivalent of an image be read out using synthetic speech. An audio file’s text alternative can be presented for people who cannot hear it, allowing them to read it. Text alternatives will eventually make it simpler to translate information into sign language or a more basic version of the same language.
What this Accessibility Rule Checks
The algorithm for this rule returns:
-
True if the element has a
<title>
code child
<svg id="target"><title>Time II: Party</title></svg>
-
True if the
<title>
child has text nested in another element.
<svg id="target"><title><g>Time II: Party</g></title></svg>
-
False if the element has no
<title>
child.
<svg id="target"></svg>
-
False if the
<title>
child is empty.
<svg id="target"><title></title></svg>
-
False if the
<title>
is a grandchild.
<svg id="target"><circle><title>Time II: Party</title></circle></svg>
-
False if the
<title>
child has only whitespace.
<svg id="target"><title> \t\r\n </title></svg>
- False if there are multiple titles and the first is empty.
<svg id="target"><title></title><title>Time II: Party</title></svg>
To avoid an unexpected tab order that would appear to miss some components entirely, a tabindex
attribute must never have a value greater than 0.
tabindex
usage with a value larger than 0 can lead to just as many issues as it fixes. The unusual tab order makes the website less logical and may give the impression that some elements have been completely skipped.
The following are some issues that tabindex
(with a value of 1 or above) results in:
-
Unexpected tab order: From the user’s perspective,
tabindex
alters the normal tab order in unanticipated ways, which could lead to confusion. -
Items can appear to be skipped entirely: Items only once appear in the tab sequence. When a user navigates through the
tabindex
items and moves on to the rest of the page, they eventually reach the location of thetabindex
items. However, the tabbing cycle skips over these links because the user already navigated past them at the start of the cycle. When visitors are unable to access items and may be unaware that they must cycle through the complete collection of links on the page to reaccess those links, incorrect tab ordering are frustrating. -
All
tabindex
items are tabbed to before any non-tabindex
items. You would need to set thetabindex
value for each and every item through the end of the updated section if you wanted to modify the tab order of the initial items AND of a section further down the page. When taken to an extreme, if a page contains 20 links and one of those links has itstabindex
set totabindex="100"
, the user will tab to that link first even if there are fewer than 100 links on the page. The tab order of sections further down the page cannot be changed unless all the links before that section’s tab order are manually changed.
What this Accessibility Rule Checks
Makes sure that explicit tabindex
attributes that are greater than 0 are never used
Markup for data tables can be tedious and complex. Make sure the summary table’s properties and the caption don’t match. There are several capabilities in screen readers that help with table navigation, but for these features to function properly, the tables must be accurately marked up.
Tables are announced in a certain way by screen readers. The potential for unclear or erroneous screen reader output exists when tables are not properly marked up.
Screen reader users may become perplexed and struggle to understand the name and function of the table if the summary and caption text for the table are identical.
What this Accessibility Rule Checks
Verifies that the wording in data tables that have both a summary and a caption is not the same.
Markup for data tables can be tedious and perplexing. There are several capabilities in screen readers that make it easier to navigate tables, but for these features to function properly, tables must be precisely marked up. Instead than utilizing a caption element, some tables visually imply a caption by employing cells with the colspan
element.
Tables are announced in a certain way by screen readers. The potential for unclear or erroneous screen reader output exists when tables are not properly marked up.
Screen reader users cannot understand the purpose of the table visually when tables are not marked up with an actual caption element but rather use a colspan
element on cells to visually indicate a caption.
What this Accessibility Rule Checks
Verifies that data tables are identified with table cells that utilize a colspan
element to visually convey a caption.
Markup for data tables can be tedious and perplexing. Tables must be semantically marked up and have the proper header structure. Table navigation is made easier by features in screen readers, but for these capabilities to function properly, the tables must be precisely marked up.
Tables are announced in a certain way by screen readers. The potential for unclear or erroneous screen reader output exists when tables are not properly marked up.
Screen reader users are unable to correctly understand the relationships between the cells and their contents visually when tables are not adequately structured and marked up semantically.
What this Accessibility Rule Checks
Verifies the correct header structure and semantic markup of data tables.