Axe Core Guide

According to WCAG 2 AA contrast ratio thresholds, all text elements must have sufficient contrast between foreground text and background colors.

Some people with impaired eyesight have little contrast, meaning there are few bright or dark areas. Everything seems approximately the same brightness, making it difficult to detect outlines, borders, edges, and particulars. Text whose luminance (brightness) is too similar to the background can be difficult to read.

Nearly three times as many individuals suffer from low vision than total blindness. About 8% of males and 0.4% of women in the United States cannot see the typical complete spectrum of colors. A person with impaired vision or color blindness cannot distinguish text against an insufficiently contrasted background.

In the background, both color transparency and opacity are taken into account.

Transparency and opacity of colors in the foreground are more challenging to detect and account for due to:

• Background and foreground colors are same.
• Gradient backgrounds in CSS
• Background colors for pseudo-elements in CSS.
• Background colors generated using CSS borders.
• Overlap by another piece in the foreground - this can present positioning challenges.
• Elements shifted out of the viewport using CSS.

What this Accessibility Rule Checks

Examines each text element to check that the contrast between the foreground text and background colors meets the WCAG 2 AAA contrast ratio requirements.

This rule does not report text elements that have a background-image, are concealed by other components, or are text images.

This check additionally looks for child elements of disabled buttons so that they can be ignored to prevent a false value.

The list of 53 Input Purposes for User Interface Components are used as the basis for the programmatic definition of the purpose for each common input field that collects user data.

For screen readers to work properly, the autocomplete attribute values must be true and applied correctly.

Inaccessible content stems from missing autocomplete values in form fields. In the absence of the necessary autocomplete attribute values, screen readers will not read the identified autocomplete form fields.

When screen readers are unable to adequately notify users about the requirements for form field interaction, users cannot successfully navigate forms.

What this Accessibility Rule Checks

The purpose of each user-information-collecting input field can be established programmatically when:

• The input field fulfills a purpose specified in the Input Purposes for User Interface Components section, and
• The content is implemented using technologies that provide support for determining the desired meaning of form input data.

Ensure that the text spacing specified by style attributes is modifiable using custom stylesheets.

When lines of text are single-spaced, many people with cognitive difficulties have difficulty following them. Providing spacing between 1.5 and 2 makes it easier for them to begin a new line after finishing the previous one.

What this Accessibility Rule Checks

Text line spacing must be modifiable by custom stylesheets.

Each form element must have a label element attached with it programmatically.

Forms must have effective form labels in order to be accessible. Form elements like as checkboxes, radio buttons, input fields, etc. are frequently self-explanatory to sighted users, even if they are not programmatically labeled. Users with screen readers require descriptive form labels to identify form fields. Adding labels to all form elements removes uncertainty and makes the product more accessible.

When form elements lack labels, screen reader users are unaware of the expected data input. Screen readers cannot determine information about input items programmatically in the absence of an established label association (or redundant text functioning as a label).

Since clicking the label activates the control, people with weak motor control do not benefit from a bigger clickable area for the control.

What this Accessibility Rule Checks

Ensures that each form element has a label associated with it programmatically.

A label element with a programmatic association must be included for each select element.

To make forms accessible, they must have clear form labels. Even if a form element isn’t programmatically named, sighted users can usually tell what it’s for when they see checkboxes, radio buttons, input fields, etc. To identify form fields, screen reader users need clear form labels. All form elements should have labels to remove confusion and make the product more accessible.

Screen reader users are in the dark about the expected input data when form elements lack labels. Without a defined label connection (or redundant text acting as a label), screen readers cannot automatically determine information about input items.

What this Accessibility Rule Checks

ensures that each select element has a label that is associated with it programmatically.

To guarantee that text is pronounced correctly for screen reader users, the language given in the HTML content must be one of the valid languages.

The default language is chosen by users when setting up a screen reader. The screen reader assumes that a webpage is in the user’s default language when the language is not selected. When visitors access the website in more than one language and speak various languages, choosing a language becomes problematic. 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 papers specify which language(s) to read, screen readers can quickly switch between these language libraries. The screen reader will read the content in the user’s default language if the language is not set, which can be confusing.

What this Accessibility Rule Checks

The value of the lang attribute must be correct.

A document’s accesskey attribute values must all be distinct. Or, to put it another way, accesskeys must not be used more than once to protect keyboard users from unpleasant surprises.

When a document’s accesskey attribute value is supplied, users can quickly activate or switch the focus to a particular element by hitting the designated key (often in tandem with the alt key). The page becomes less accessible as a result of duplicating the values for the accesskey attribute.

Make sure the value of each defined accesskey is distinct and does not interfere with any screen reader or default browser shortcut keys.

Users who must use alternative keyboards or input devices serving as keyboard emulators, users who have problems tracking a pointer, or users who are blind or have low eyesight and cannot employ eye-hand coordination-required devices like mice, cannot operate the content.

What this Accessibility Rule Checks

Makes certain that every element on the page with an accesskey attribute has a different value.

An image map consists of a single image with numerous clickable sections. Because screen readers cannot translate graphics into text, an image map, like all images, must contain alternate text for each of the distinct clickable parts, as well as for the larger image itself.

In the absence of alternate text, screen readers often announce the image’s filename. Filenames do not accurately describe images and are therefore inconvenient for screen reader users.

What this Accessibility Rule Checks

Ensures that image map area elements have alternate text.

Not all ARIA role-attribute combinations are valid. This rule ensures that each role has the required qualities.

Using ARIA attributes in roles where they are not permitted can impair web page accessibility. Using an improper role-attribute combination will have no effect on application accessibility at best and may trigger behavior that blocks accessibility for entire areas of an application at worst.

When ARIA attributes are used on HTML elements that do not conform to WAI-ARIA 1.1, they interfere with the semantics of the elements, causing assistive technology products to display nonsensical user interface (UI) information that does not represent the document’s true UI.

What this Accessibility Rule Checks

Checks that each element with an ARIA role is using only the ARIA attributes that are permitted for that role.

aria-braille attributes must have a non-braille equivalent.

WAI-ARIA requires that the aria-braillelabel attribute is only ever used on elements with an accessible name, such as from aria-label. Similarly, aria-brailleroledescription is required to only ever be used on elements with aria-roledescription.

ARIA braille attributes were introduced to allow adjusting how labels and role descriptions are rendered on a braille display. They cannot be the only attribute providing a label, or a role description. When used without a corresponding label or role description ARIA says to ignore these attributes, although this may not happen consistently in screen readers and other assistive technologies.

How to Fix this Issue

• The aria-braillelabel or aria-brailleroledescription attribute may have been placed on the wrong element, such as a parent or child of the correct element. The attribute should be put on a different element.
• The element with aria-braillelabel attribute needs an aria-label attribute or other attribute that gives it an accessible name.
• The element with aria-brailleroledescription attribute needs a aria-roledescription attribute.
• The aria-braillelabel or aria-brailleroledescription attribute serves no function and should be removed.

What this Accessibility Rule Checks

Checks that aria-braillelabel is only used on elements with a non-empty label, and that aria-brailleroledescription is only used on elements with a non-empty aria-roledescription.