noopener

noopener is a link relation type used in HTML to improve security when hyperlinks open in a new browsing context, typically with target="_blank".

When a link includes rel="noopener", the opened page's window.opener is set to null. This prevents the new page from having a persistent reference to the original page, reducing the risk of tabnabbing where an attacker could redirect the original page to a phishing site.

In practice, developers use: <a href="..." target="_blank" rel="noopener">Link</a>. To also avoid leaking the referrer information, rel="noopener noreferrer" is commonly recommended. Some browsers implement noreferrer such that it implies noopener, but relying on that behavior is less portable than including both values explicitly.

Compatibility is high among modern browsers, including Chrome, Firefox, Edge, and Safari. While older or nonstandard browsers may ignore rel="noopener", the practice remains widely adopted as a defensive measure.