# id attribute value must be unique

> Canonical HTML version: https://rocketvalidator.com/accessibility-validation/axe/4.7/duplicate-id
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

To avoid assistive technology missing the second instance, the value supplied to an `id` property must be distinct. In other words, `id` attributes may not be used more than once to distinguish one element from another within the same document.

Elements on a page are uniquely identified via the ID attribute. It makes no sense to make a second `id`.

Duplicate `id`s can make labels for forms, table header cells, etc. inaccessible since screen readers and client-side scripts pass over the second iteration. They are typical markup validation mistakes that, if they do not damage accessibility, can reduce potential causes of accessibility issues.

Those who are familiar with client-side scripting are aware that when an ID is reused, the script normally only reacts to the first instance of that `id` use. Similar to this, assistive technology might only appropriately reference the first `id` when referencing an `id`.

<h3>What this Accessibility Rule Checks</h3>

Makes certain that every element on the page with an id attribute has a distinct value for the `id` attribute.