Use IDs to identify and target unique elements.
Designers and developers use unique identifiers (IDs) to optimize sites for accessibility and to extend site functionality with custom code. IDs can be useful for linking, scripting, or styling (with CSS).
Using the same ID on more than one element, however, may cause screen readers to malfunction, as they’ll only target the first element with the shared ID, preventing screen reader users from accessing the later elements and properly navigating the webpage.
Learn more about identifying and fixing duplicate element IDs.
WCAG Reference: Success Criterion 4.1.1: Parsing