What is adnxs.com and why you should block it
adnxs.com is the domain of Microsoft's advertising platform Xandr. Learn how it tracks you and how to protect yourself.
Drafted by automation from the sources listed at the end of this page, and reviewed before publishing. The sources are the part that matters: check them.
What is adnxs.com?
adnxs.com is the domain associated with Xandr, a digital advertising platform owned by Microsoft. Originally, Xandr was created by AT&T in 2018 to consolidate its advertising assets, including AppNexus (an ad tech company). In 2022, Microsoft acquired Xandr for about $1 billion, and later folded it into its Microsoft Advertising division.
Who operates the domain?
The domain is operated by Microsoft Advertising (formerly Xandr). The infrastructure behind adnxs.com is used to buy and sell digital ads in real time, connecting advertisers with publishers of websites and apps.
How does it collect browsing data?
When you visit a site that uses Xandr’s platform, your browser may make a request to adnxs.com. This allows Xandr to:
- Identify your device via cookies (or similar local storage).
- Log your visits, clicks, and other interactions.
- Build a profile of your interests and browsing habits.
- Use that information to serve targeted ads on other sites.
Xandr may also combine this data with other sources, such as data from telecom operators (AT&T’s history) or data partners, to enrich the profile.
Why do privacy tools block adnxs.com?
Blocklists like EasyList and Peter Lowe’s List include adnxs.com for several reasons:
- Invasive tracking: Xandr is one of the largest ad trackers, monitoring users across a large portion of the web.
- Behavioral advertising: The purpose is to serve ads based on your behavior, which many consider a privacy violation.
- Lack of clear consent: Often, tracking occurs without the user having given explicit consent, especially on sites that use third-party cookies.
Limitations of DNS blocking
Blocking the domain prevents the browser from connecting to Xandr’s ad servers. This reduces tracking and ad display. However, it’s important to know:
- Does not remove all ads: Some ads may be served directly from the same domain as the content (e.g., a site might host ads on its own subdomain). In that case, blocking adnxs.com won’t remove them.
- Does not hide your IP: Blocking doesn’t affect your connection to the site you visit; your IP address is still visible to the site and network.
- May break functionality: Some sites might use Xandr’s infrastructure for other functions (like login or personalization). Blocking can cause loading errors.
How to protect yourself?
You can block adnxs.com using browser extensions like uBlock Origin, which use frequent blocklists. You can also use DNS-level blocking, such as Pi-hole or DNS services that filter trackers.
Blocking is one layer of protection, not the only one. Consider also using browsers with built-in protection (like Firefox with Enhanced Tracking Protection) and reviewing privacy settings of sites.
Conclusion
adnxs.com represents Microsoft’s advertising infrastructure, and blocking is an effective measure to reduce tracking. However, remember its limitations. For more complete protection, combine blocking with other privacy practices.
This article is informative and based on public facts about Xandr/Microsoft Advertising.