Guias de acessibilidade para grave

tabindex="-1" cannot be present in <frame> and <iframe> elements with focusable content.

The browser is unable to move the focus to the content included in a frame when it has a negative tabindex. This stops keyboard navigation from skipping all of its content, and if the frame is scrollable, it also prevents the focus from moving to any element from which the frame may be scrolled.

What this Accessibility Rule Checks

Examine all frame and iframe elements that contain a negative tabindex value, such as tabindex="-1". If there are any such frames, make sure they don’t have nested frames that do contain focusable items.

To help screen reader users understand the contents of each frame or iframe element in the document, each element must have a distinct title.

A frame title is used by screen reader users to describe the contents of the frame. If the frames are not identified with a title element, navigating across frames and iframes can soon become challenging and confusing for users of this technology.

Users of screen readers can choose to display a list of all the titles for the frames on a page. Users can locate the frame they’re looking for more quickly by adding descriptive, distinctive labels. Without titles, moving between frames can become challenging and perplexing very quickly. Screen readers will instead provide information such as “frame,” “javascript,” the filename, or the URL if there is no title specified. This information won’t usually be particularly useful.

What this Accessibility Rule Checks

Make sure that the title attribute on every iframe and frame element is distinct and not empty.

When used in a document, the frame or iframe element’s title attribute must not be empty in order to provide context for users of screen reader software.

Users of screen readers depend on the title of a frame to describe its contents. If the HTML for a frame or iframe element lacks a title attribute, navigating within the element can be a frustrating and time-consuming experience for users of this technology.

Users of screen readers can see a list of the frames on a page and their respective titles. Providing each frame with a distinct, descriptive label facilitates easy navigation. Without titles, it’s easy to get lost trying to jump from one frame to the next. Screen readers will instead provide information like “frame,” “JavaScript,” the filename, or the URL if no title is provided. This data is unlikely to be useful in most situations.

What this Accessibility Rule Checks

Make sure the title attribute of every iframe and frame element is both distinct and not empty.

For multilingual screen reader users who would prefer a language other than the default, the HTML document element must have a valid lang property or match to a valid lang code.

The default language is chosen by users when setting up a screen reader. The screen reader uses the user’s default language preference when a webpage’s language is not specified. When people visit websites in more than one language and speak various languages, language settings become a problem. To ensure that website text is pronounced accurately, a language must be specified and validated.

Based on the pronunciation and traits of each language, screen readers employ distinct sound libraries for each one. If the documents state which language(s) to read when, screen readers can effortlessly switch between these language libraries. The screen reader will read the page in the user’s default language if the language is not set, which will result in an odd accent. When screen readers are utilizing the incorrect language library, nothing can be understood.

What this Accessibility Rule Checks

Ensures that the lang attribute is present in every HTML document.

For multilingual screen reader users who may prefer a language different than the default, the HTML content must contain a valid lang attribute or correlate to a valid lang code.

Users choose a default language when configuring a screen reader. If the language of a webpage is not provided, the screen reader uses the user’s default language. Language settings are a problem for users who speak different languages and visit websites in multiple languages. It is critical to declare a language and guarantee that it is valid in order for website text to be properly pronounced.

Screen readers employ various sound libraries for each language based on its pronunciation and characteristics. Screen readers can readily switch between these language libraries, but only if the documents specify which language(s) they should read. If no language is supplied, the screen reader reads the content in the user’s default language, which results in a perplexing accent! When screen readers use the incorrect language library, it is difficult to understand anything.

What this Accessibility Rule Checks

Ensures that every HTML document contains a lang or xml:lang property with a valid value.

The visible label of interactive items labeled through their content must be included in their accessible name.

This rule applies to any element with the following attributes:

• a semantic role that is a widget that supports name from content,
• visible text, and
• an aria-label or aria-labelledby attribute.

button, checkbox, gridcell, link, menuitem, menuitemcheckbox, menuitemradio, option, radio, searchbox, switch, tab, and treeitem are widget roles that support name from content.

The whole visible text content of the target element either matches its accessible name or is contained within it.

Leading and trailing whitespace and case sensitivity differences should be disregarded.

Users using speech input can interact with a web page by saying the visible text labels of menus, links, and buttons.

Voice input users are confused when they utter a visible text label, but the speech command does not work since the accessible (programmatic) name of the component does not match the visible label. When a user interface component contains a visible text label — whether the label is actual text or a picture of text — that text must also appear in the component’s accessible (programmatic) name. When the visual label and accessible (programmatic) name for interactive components are synchronized, users using speech input can engage with those components successfully.

What this Accessibility Rule Checks

For any user interface element with a visible text label, the accessible name must match (or include) the label’s visible text.

Using the title or aria-describedby properties, form <input> elements may be given titles (but not both). The purpose of these qualities is to convey more information, such as a tip.

These properties are used to convey additional information, such as a hint. Hints are exposed differently to accessibility APIs than labels, which can cause issues with assistive technologies.

When form inputs such as text entry fields, radio buttons, check boxes, and select menus do not have labels other than the title and aria-describedby attribute values, screen readers perceive the material as advisory only. The labels provided by the title and aria-describedby attributes are insufficient to create a real label that can be inferred programmatically from the input form element’s code.

What this Accessibility Rule Checks

Ensures that every <input> that requires a label has a label other than title or aria-describedby.

Makes sure that people who can’t differentiate colors can tell when text is a link by checking that the link has either a distinct style that doesn’t depend on color or a contrast difference of more than 3:1, which tells you that manual testing is needed.

Some people with low vision have low contrast, which means there aren’t many bright or dark areas. Everything looks about the same brightness, which makes it hard to see details, edges, borders, and outlines. It can be hard to read text that is the same brightness as the background.

There are almost three times as many people with low vision as there are who are totally blind. One in twelve people, or about 8% of men and 0.4% of women in the US, has a color deficiency. People with low vision or color blindness can’t tell what the text is against a background that doesn’t have enough contrast.

When there isn’t a 3:1 color contrast between the color of the link text and the color of the text around it, people with low vision or low contrast can’t tell by looking that the text is meant to be a link.

What this Accessibility Rule Checks

Checks that all links in blocks of text have a color difference of at least 3:1 from the text around them, so that people who can’t tell the colors apart can still find the link.

This rule looks at some of the most common ways to tell a link from the text around it, such as underlining, font styling, a border, or a background. No rule has been broken if the link has its own style that doesn’t depend on color (pass). There is a violation if the link doesn’t have a clear style and the contrast is less than 3:1. (fail). When the link doesn’t have a distinct style and the contrast difference is 3:1 or higher, you must check that the link has a distinct style when you focus on it or hover over it. This can’t be reliably done by a computer, so you have to do it by hand.

When used as links, link text and alternative text for images must be recognizable by screen readers, have no duplicate labels, and be focusable.

• Accessibility is hindered by inaccessible link components, as they are a crucial component of a website.
• Users who traverse a webpage using only the keyboard (and no mouse) can only click on links that can gain programmed emphasis. Inaccessible to these users is any link that cannot gain programmatic focus.
• Similar to sighted people, screen reader users must know where a link leads. This information is provided via inner link text, albeit it will not be utilized if a screen reader cannot access it.
• Only the links and form components that can get programmatic focus can be activated by keyboard users, including those with visual impairments or those who cannot use a mouse. Keyboard users cannot access events activated only by other sorts of focus, such as onmouseover events that depend on the mouse hover focus. By default, only links and form elements receive keyboard emphasis. Add tabindex="0" to items that are not links or form components to make them focusable.

What this Accessibility Rule Checks

Ensures that each link’s name is accessible.