IDs used in ARIA and labels must be unique
How to Fix the Problem
Rename any duplicate ID values.
Duplicate IDs are common validation errors that may break the accessibility of labels, e.g., form fields, table header cells.
To fix the problem, change an ID value if it is used more than once to be sure each is unique. Unique ID's differentiate each element from another and prevent invalid markup, wherein only the first instance gets acted upon by client-side scripting, or where assistive technologies typically only reference the first one accurately.
Why it Matters
Duplicate IDs are common validation errors that may break the accessibility of labels, e.g., ARIA elements, form fields, table header cells.
Unique ID's differentiate each element from another and prevent invalid markup, wherein only the first instance gets acted upon by client-side scripting, or where assistive technologies typically only reference the first one accurately.
Rule Description
The value assigned to an id
attribute used in ARIA or in form
labels must be unique to prevent the second instance from being overlooked by
assistive technology. Put another way; ID values used in ARIA and in labels
may not be used more than once in the same document to differentiate each
element from another.
The Algorithm (in simple terms)
Ensures every ID used in ARIA attributes and for
attribute on a
label is unique