By default, web browsers perform https://developer.mozilla.org/en-US/docs/Web/Performance/dns-prefetch/[DNS prefetching] to reduce latency due to DNS resolutions required when an user clicks links from a website page.


For instance on example.com the hyperlink below contains a cross-origin domain name that must be resolved to an IP address by the web browser:

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<a href="https://otherexample.com">go on our partner website</a>
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It can add significant latency during requests, especially if the page contains many links to cross-origin domains. DNS prefetch allows web browsers to perform DNS resolving in the background before the user clicks a link. This feature can cause privacy issues because DNS resolving from the user's computer is performed without his consent if he doesn't intent to go to the linked website.


On a complex private webpage, a combination "of unique links/DNS resolutions" can indicate, to a eavesdropper for instance, that the user is visiting the private page.
