Can Multiple HTML Elements Share the Same ID, and What Are the Consequences?

Can Multiple Elements Share the Same ID Selector?

Despite the explicit guidelines from W3C stating that ID attributes must be unique, browsers often exhibit different behaviors when encountering duplicate IDs.

The example provided illustrates this discrepancy, where two elements with the same ID respond to the CSS selector. This is primarily due to browsers' tendency to "fail silently" and attempt to interpret the developer's intent, even when it violates HTML standards.

However, it's crucial to note that deviating from the specifications can lead to unforeseen consequences:

• document.getElementById('red') will only return the first element with that ID.
• Cross-browser compatibility issues may arise as browser implementations vary.

Recommendation:

For optimal results, it's strongly discouraged to assign duplicate IDs to elements. Instead, utilize class names to target multiple elements with the same CSS styles. Classes are explicitly designed for this purpose.

Alternative Approach for Multiple ID Selection:

If absolutely necessary, attribute selectors can be used to select multiple elements with the same ID:

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

However, this approach is not supported in IE7 and below.

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