Noopener: Protecting Your Site from Sneaky Security Risks

What Is Noopener and Why It Matters

The noopener attribute is a value applied to the rel attribute in HTML anchor tags (<a>) when linking to external websites, especially when using target="_blank" to open links in new tabs or windows.

When a visitor clicks a link that opens in a new tab without noopener, the new page gains partial access to your page through the JavaScript window.opener object. This creates what security experts call the “reverse tabnabbing vulnerability”—a serious security risk that many marketers and even developers overlook.

Many marketing professionals focus exclusively on the promotional aspects of their links without considering the technical implications. This oversight can lead to serious security vulnerabilities and performance issues that ultimately impact user experience and brand reputation.

Security Implications of Omitting Noopener

The security vulnerability created by omitting noopener is more serious than most marketers realize. Here’s what can happen when you don’t use this attribute with external links that open in new tabs:

• The linked website can access your page through the window.opener object
• It can redirect your original page to a different URL, potentially a phishing site
• The malicious page can run resource-intensive scripts affecting your page’s performance
• User session information might be accessible in certain scenarios

This vulnerability, known as “reverse tabnabbing,” allows a malicious site to redirect your original page to a fake version of itself or another trusted site. When users return to what they think is your website, they might encounter a convincing replica asking for login credentials or other sensitive information.

Real-world examples of this vulnerability being exploited are numerous but often go unreported or unnoticed. Major brands have unknowingly exposed their users to phishing attacks simply by overlooking this small but crucial attribute.

Performance Benefits of Using Noopener

Beyond security, there’s another compelling reason to implement noopener: performance improvement. When you open a link in a new tab without noopener, the new page runs in the same process as the opener page in many browsers. This creates performance implications that affect user experience:

• The linked page can slow down your original page’s performance
• Heavy JavaScript on the new page can affect your page’s responsiveness
• Both pages compete for the same processing resources
• Page load time and responsiveness can be significantly impacted

By adding the noopener attribute, you force the browser to treat the new tab as a separate process, preventing performance degradation on your original page. This may seem like a minor optimization, but when aggregated across all your external links, the performance improvement can be substantial.

How to Implement Noopener Correctly

Implementing noopener is straightforward once you understand the syntax. Here’s how to do it properly:

Basic Implementation

The simplest way to add noopener to a link that opens in a new tab:

<a href="https://example.com" target="_blank" rel="noopener">Link text</a>

Combined with Other Rel Attributes

You can combine noopener with other rel attributes by separating them with spaces:

<a href="https://example.com" target="_blank" rel="noopener noreferrer">Link text</a>

Implementing in Content Management Systems

Most modern CMS platforms like WordPress, Shopify, or Wix automatically add noopener to external links that use target=”_blank”. However, custom themes or older CMS versions might not have this feature. Here’s how to check and implement in various systems:

JavaScript Solution for Retroactive Implementation

If you need to add noopener to an existing site with many external links, this JavaScript snippet can help:

document.querySelectorAll('a[target="_blank"]').forEach(link => {
  if (!link.rel || !link.rel.includes('noopener')) {
    link.rel = link.rel ? link.rel + ' noopener' : 'noopener';
  }
});

This code automatically adds the noopener attribute to all links with target=”_blank” that don’t already have it.

Noopener vs. Noreferrer: Understanding the Difference

Noopener and noreferrer are often used together, but they serve different purposes. Understanding the distinction helps you make informed decisions about which to implement:

While noopener focuses on security by breaking the connection between pages, noreferrer goes further by also hiding referral information. This means the destination site won’t know where their traffic came from.

When to Use Each Attribute

• Use noopener when you want to protect your site from reverse tabnabbing while still letting the destination know users came from your site
• Use noreferrer when you want to hide the fact that users came from your site (this also implicitly includes noopener functionality in most browsers)
• Use both for maximum compatibility across all browsers and complete security

Many marketing professionals default to using both attributes together (rel="noopener noreferrer") as a best practice to ensure maximum security and compatibility across all browsers.

SEO Impact of Noopener Implementation

A common question among marketing professionals is whether using noopener affects SEO. The good news is that noopener itself has no negative impact on search engine optimization. In fact, implementing it can indirectly benefit your SEO efforts:

• Google and other search engines recognize noopener as a security best practice
• Improved page performance (which noopener helps with) is a ranking factor
• Using noopener doesn’t affect link equity passing to external sites
• It doesn’t change how search engines interpret your outbound links

Unlike noreferrer, which prevents referral information from being passed, noopener maintains normal referral data flow. This means the destination site still receives the information that traffic came from your website in their analytics, and search engines still understand the relationship between the sites.

If you’re focused on building a technically sound website that follows best practices (which search engines reward), implementing noopener is a small but meaningful step in that direction.

Common Mistakes When Using Noopener

Even when trying to implement noopener correctly, marketers and developers often make several common mistakes that diminish its effectiveness:

1. Applying to Internal Links

While not harmful, adding noopener to internal links (links to pages on your own domain) is unnecessary. The security vulnerability only exists with external domains.

2. Forgetting to Add target=”_blank”

The noopener attribute only makes sense when used with links that open in new tabs or windows (target="_blank"). If the link doesn’t open in a new tab, there’s no security risk to address.

3. Incorrect Syntax

Common syntax errors include:

• Using rel="no-opener" (with a hyphen)
• Writing rel="noopener," (with a comma)
• Misspelling as rel="nopoener"

4. Conflicting with Tracking Code

Some marketing tracking scripts modify outbound links and may inadvertently remove or override the noopener attribute. Always test your links after implementing tracking codes.

Frequently Asked Questions About Noopener