What Happens When Multiple HTML Elements Share the Same ID?

ID Selectors and Multiple HTML Elements

While HTML5 dictates that ID attributes are unique identifiers for elements on a page, the practical application in browsers deviates from this rule. Browsers strive to interpret the intent of HTML and execute code accordingly, even if it results in non-standard behavior.

However, assigning multiple elements the same ID can lead to unexpected consequences. Browsers may only acknowledge the first element with that ID, resulting in unpredictable interactions. Additionally, inconsistencies can arise across different browsers, leading to potential issues if your page targets multiple user environments.

Alternative Approach

To avoid these inconsistencies, use CSS class names instead when targeting multiple elements. Class names are designed to group elements that share common styles or functionality. This approach ensures predictable behavior across browsers and maintains the consistency expected from ID attributes.

Attribute Selectors for Multiple IDs

If absolutely necessary to select multiple elements with the same ID, you can utilize attribute selectors. For example:

document.querySelectorAll('p[id="red"]');

However, it's crucial to note that attribute selectors are not supported in IE7 or earlier browsers, limiting their compatibility.

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