What Is the s.w.org DNS Prefetch in WordPress?
WordPress adds a dns-prefetch link to s.w.org on every page. It leaks browsing data to an external server. Here's what it does and how to remove it.
View the source of your WordPress site and look near the top of <head>. You’ll probably find this line:
<link rel='dns-prefetch' href='//s.w.org' />That one tag tells every visitor’s browser to perform a DNS lookup for s.w.org — a WordPress CDN server — before it’s even needed. On every page. For every visitor. Whether your site uses emojis or not.
It’s been a source of debate in the WordPress community for years, and it has both performance and privacy implications.
What is DNS prefetching?
DNS prefetching is a browser hint. The <link rel="dns-prefetch"> tag tells the browser: “you might need to connect to this domain soon, so resolve its IP address now.” The idea is to save the 50-100ms a DNS lookup takes when the resource is actually requested later.
WordPress adds a DNS prefetch for s.w.org because that’s where emoji images are hosted. If a visitor’s browser can’t render emojis natively, WordPress loads image replacements from this CDN. The prefetch is meant to speed up that potential load.
The problem: virtually every modern browser handles emojis natively. The CDN images are almost never loaded. So you’re making every visitor perform a DNS lookup for a server they’ll never connect to.
Why should you care?
Privacy concern. A DNS lookup is a network request. Even though it doesn’t download any content, it tells your visitor’s DNS resolver (often their ISP) that they visited a site connected to s.w.org. For European sites under GDPR, this is an external data transfer your visitors didn’t consent to. WordPress Trac ticket #40426 flagged this as a privacy concern years ago.
Wasted network round-trip. On mobile connections with high latency, DNS lookups can cost 50-100ms. That’s time spent resolving a domain your visitors will never actually connect to. It’s small, but it’s an unnecessary waste on every page load.
It’s a WordPress fingerprint. The s.w.org prefetch tells anyone viewing your source code that you’re running WordPress. While not a major security issue by itself, it’s one more signal for automated scanners.
The quick fix
// Remove s.w.org DNS prefetch
remove_action( 'wp_head', 'wp_resource_hints', 2 );Warning: This removes all default WordPress resource hints, not just s.w.org. If you want to keep other prefetch hints while removing only s.w.org, use the filter approach:
// Remove only s.w.org from DNS prefetch hints
add_filter( 'wp_resource_hints', function( $urls, $relation_type ) {
if ( 'dns-prefetch' === $relation_type ) {
$urls = array_filter( $urls, function( $url ) {
return strpos( $url, 's.w.org' ) === false;
});
}
return $urls;
}, 10, 2 );The one-click solution
Ovanap Admin Toolkit includes Stop pinging WordPress.org under Admin Toolkit → Features → Performance. One switch removes the s.w.org prefetch while preserving any other resource hints your theme or plugins might add.
What happens after you fix this?
- No more DNS lookup to s.w.org for every visitor on every page
- One fewer
<link>tag in your HTML<head> - Improved GDPR posture — no external DNS requests without consent
- One fewer WordPress fingerprint in your page source
FAQ
Will removing this break emojis on my site?
No. Modern browsers render emojis natively using the operating system’s emoji font. The s.w.org CDN is only used as a fallback for very old browsers. If you’ve also disabled the emoji script (which you should), the prefetch is doubly unnecessary.
Is this related to the emoji script removal?
Yes. If you remove the WordPress emoji script, the DNS prefetch for s.w.org becomes completely pointless — the code that would use the CDN no longer loads. However, WordPress adds them separately, so you need to remove both independently.
Does this affect Google Fonts or other DNS prefetch hints?
Only if you use the remove_action method, which removes all default hints. The wp_resource_hints filter method (shown above) only targets s.w.org specifically. Ovanap Admin Toolkit uses the filter approach for precision.
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