html-aria

WAI-ARIA utilities for HTML based on the ARIA 1.3 spec and latest HTML in ARIA recommendations (Dec 2024). Lightweight (5k gzip), performant, and zero dependencies.

⚠️ This is in beta and subject to change.

VS other libraries

aria-query

• html-aria supports ARIA 1.3 while aria-query is still on ARIA 1.2
• html-aria is designed to reduce effort and minimize error for common tasks (e.g. determining ARIA roles from HTML). aria-query is a general purpose replication of the ARIA spec that requires more understanding and more boilerplate code.
• html-aria is more performant (100× faster) due to aria-query constantly redoing work.
• html-aria is smaller, weighing only ~5k gzip (aria-query is ~13k gzip)
• html-aria respects more nuance in the spec such as improved role detection from HTML and HTML-aware aria-* attributes

Setup

npm i html-aria

API

getRole()

Get a valid ARIA role from HTML. This is the core API.

import { getRole } from "html-aria";

getRole(document.createElement("article")); // "article"
getRole({ tagName: "input", attributes: { type: "checkbox" } }); // "checkbox"
getRole({ tagName: "div", attributes: { role: "button" } }); // "button"

It’s important to note that inferring ARIA roles from HTML isn’t always straightforward! There are 3 types of role inference:

1. Tag map: 1 tag → 1 ARIA role.
2. Tag + attribute map: Tags + attributes are needed to determine the ARIA role (e.g. input[type="radio"] → radio)
3. Tag + DOM tree: Tags + DOM tree structure are needed to determine the ARIA role.

Learn more.

getSupportedRoles()

The spec dictates that certain elements may NOT receive certain roles. For example, <div role="button"> is allowed (not recommended, but allowed), but <select role="button"> is not. getSupportedRoles() will return all valid roles for a given element + attributes.

import { getSupportedRoles } from "html-aria";

getSupportedRoles(document.createElement("img")); // ["none", "presentation", "img"]
getSupportedRoles({ tagName: "img", attributes: { alt: "Image caption" } }); //  ["button", "checkbox", "link", (15 more)]

getSupportedAttributes()

For any element, list all supported aria-* attributes, including attributes inherited from superclasses. This takes in an HTML element, not an ARIA role, because in some cases the HTML element actually affects the list (see full list).

import { getSupportedAttributes } from "html-aria";

getSupportedAttributes({ tagName: "button" }); // ["aria-atomic", "aria-braillelabel", …]

If you want to look up by ARIA role instead, just pass in a placeholder element:

getSupportedAttributes({ tagName: "div", attributes: { role: "combobox" } });

There’s also a helper method isSupportedAttribute() to test individual attributes:

import { isSupportedAttribute } from "html-aria";

isSupportedAttribute({ tagName: "button" }, "aria-pressed"); // true
isSupportedAttribute({ tagName: "button" }, "aria-checked"); // false

It’s worth noting that HTML elements may factor in according to the spec—providing the role isn’t enough. See aria-* attributes from HTML.

isValidAttributeValue()

Some aria-* attributes require specific values. isValidAttributeValue() returns false if, given a specific aria-* attribute, the value is invalid according to the spec.

import { isValidAttributeValue } from "html-aria";

// string attributes
// Note: string attributes will always return `true` except for an empty string
isValidAttributeValue("aria-label", "This is a label"); // true
isValidAttributeValue("aria-label", ""); // false

// boolean attributes
isValidAttributeValue("aria-disabled", true); // true
isValidAttributeValue("aria-disabled", false); // true
isValidAttributeValue("aria-disabled", "true"); // true
isValidAttributeValue("aria-disabled", 1); // false
isValidAttributeValue("aria-disabled", "disabled"); // false

// enum attributes
isValidAttributeValue("aria-checked", "true"); // true
isValidAttributeValue("aria-checked", "mixed"); // true
isValidAttributeValue("aria-checked", "checked"); // false

⚠️ Be mindful of cases where a valid value may still be valid, but invoke different behavior according to the ARIA role, e.g. mixed behavior for radio/menuitemradio/switch

Reference

ARIA roles from HTML

This outlines the requirements to adhere to the W3C spec when it comes to inferring the correct ARIA roles from HTML. Essentially, there are 3 types of inference:

1. Tag map: 1 tag → 1 ARIA role.
2. Tag + attribute map: Tags + attributes are needed to determine the ARIA role (e.g. input[type="radio"] → radio)
3. Tag + DOM tree: Tags + DOM tree structure are needed to determine the ARIA role.

Here are all the HTML elements where either attributes, hierarchy, or both are necessary to determine the correct role. Any HTML elements not listed here follow the simple “tag map” approach (keep in mind that aria-* attributes may not follow the same rules!).

Note: — = no corresponding role

aria-* attributes from HTML

Further, a common mistake many simple accessibility libraries make is mapping aria-* attributes to ARIA roles. While that mostly works, there are a few exceptions where HTML information is needed. That is why getSupportedAttributes() takes an HTML element. Here is a full list:

Note: — = no corresponding role. Also worth pointing out that in other cases, global aria-* attributes are allowed, so this is unique to the element and NOT the ARIA role.

Technical deviations from the spec

SVG

SVG is tricky. Though the spec says <svg> should get the graphics-document role by default, browsers chose chaos. Firefox 134 displays graphics-document, Chrome 131 defaults to image (previously it returned nothing, or other roles), and Safari defaults to generic (which is one of the worst roles you could probably give it).

Since we have 1 spec and 1 browser agreeing, this library defaults to graphics-document. Though the best answer is SVGs should ALWAYS get an explicit role.

Ancestor-based roles

In regards to ARIA roles in HTML, the spec gives non-semantic roles to <td>, <th>, and <li> UNLESS they are used inside specific containers (table, grid, or gridcell for <td>/<th>; list or menu for <li>). This library assumes they’re being used in their proper containers without requiring the ancestors array. This is done to avoid the footgun of requiring missable configuration to produce accurate results, which is bad software design.

Instead, the non-semantic roles must be “opted in” by passing an explicitly-empty ancestors array:

import { getRole } from "html-aria";

getRole({ tagName: "td" }, { ancestors: [] }); // undefined
getRole({ tagName: "th" }, { ancestors: [] }); // undefined
getRole({ tagName: "li" }, { ancestors: [] }); // "generic"

FAQ

Why the { tagName: string } object syntax?

Most of the time this library will be used in a Node.js environment, likely outside the DOM (e.g. an ESLint plugin traversing an AST). While most methods also allow an HTMLElement as input, the object syntax is universal and works in any context.

What’s the difference between “no corresponding role” and the none role?

From the spec:

No corresponding role

The elements marked with No corresponding role, in the second column of the table do not have any implicit ARIA semantics, but they do have meaning and this meaning may be represented in roles, states and properties not provided by ARIA, and exposed to users of assistive technology via accessibility APIs. It is therefore recommended that authors add a role attribute to a semantically neutral element such as a div or span, rather than overriding the semantics of the listed elements.

none role

An element whose implicit native role semantics will not be mapped to the accessibility API. See synonym presentation.

In other words, none is more of a decisive “this element is presentational and can be ignored” labeling, while “no corresponding role” means “this element doesn’t have predefined behavior that can be automatically determined, and the author should provide additional information such as explicit roles and ARIA states and properties.”

In html-aria, “no corresponding role” is represented as undefined.

What is the difference between “unsupported attributes” and “prohibited attributes?”

In the spec, you’ll find language describing both roles and attributes in 4 categories:

1. Supported and recommended: valid and recommended to use
2. Supported but not recommended: valid, but may cause unpredictable behavior
3. Unsupported, but not prohibited: these are omitted both from supported and prohibited lists
4. Unsupported and prohibited: explicitly prohibited

As stated in Project Goals, html-aria aims to not conflate non-normative recommendations as normative guidelines. So in the API, getSupportedRoles() and getSupportedAttributes() will return 1 and 2, but not 3 or 4.

While there is a technical distinction between 3 and 4, for the purposees of html-aria they’re treated the same.

About

Project Goals

1. Get annoyingly-close to the WAI-ARIA specification while remaining user-friendly
2. Don’t be opinionated