Attributes that start with `aria-` must be defined.

Rule ID	Widget 5
Definition	Elements with the attributes that start with `aria-` must be a valid ARIA property or state.
Purpose	ARIA attributes must be defined properties or states to accurately describe web content to users of assistive technologies, especially screen reader users
Required	Yes for HTML5 and ARIA Techniques ruleset mapping
WCAG Success Criteria	4.1.2 Name, Role, Value (Level A, Primary Success Criterion) Other Related Success Criterion: 1.3.1 Info and Relationships (Level A) 3.3.2 Labels or Instructions (Level A)
Rule Category	Widgets/Scripting
Scope	Element
Target Resources	Elements with aria attributes `[aria-atomic]` `[aria-autocomplete]` `[aria-busy]` `[aria-checked]` `[aria-controls]` `[aria-describedby]` `[aria-disabled]` `[aria-dropeffect]` `[aria-expanded]` `[aria-flowto]` `[aria-grabbed]` `[aria-haspopup]` `[aria-hidden]` `[aria-invalid]` `[aria-label]` `[aria-labelledby]` `[aria-level]` `[aria-live]` `[aria-multiline]` `[aria-multiselectable]` `[aria-orientation]` `[aria-owns]` `[aria-pressed]` `[aria-readonly]` `[aria-relevant]` `[aria-required]` `[aria-selected]` `[aria-sort]` `[aria-valuemax]` `[aria-valuemin]` `[aria-valuenow]` `[aria-valuetext]`
Techniques	Use defined ARIA properties and states in the ARIA specification. Check W3C WAI Accessible Rich Internet Applications specifications for allowed values for ARIA attributes.
Informational Links	Accessible Rich Internet Applications (WAI-ARIA) 1.2 Specification: Supported Property and States G108: Using markup features to expose the name and role, allow user-settable properties to be directly set, and provide notification of changes ARIA5: Using WAI-ARIA state and property attributes to expose the state of a user interface component ARIA Authoring Practices MDN Web Docs: ARIA Web Fundamentals: Introduction to ARIA

Attributes that start with aria- must be defined.

Attributes that start with `aria-` must be defined.