Last month, I noticed the same pair of sneakers following me across every website I visited. From news sites to social media, those exact shoes kept appearing in banner ads. The culprit? Criteo, one of the world's largest advertising technology companies that tracks over 700 million users daily across more than 20,000 websites.

Criteo is a French advertising company that specializes in retargeting – showing you ads for products you've previously viewed or searched for online. When you browse AliExpress, Amazon, or thousands of other e-commerce sites, Criteo's tracking pixels are quietly collecting data about your shopping behavior to create detailed profiles for targeted advertising.

How Criteo's tracking network actually works

Criteo operates what's essentially a massive surveillance network disguised as an advertising service. According to privacy researcher Steven Englehardt's 2016 study, Criteo ranks among the top 10 most prevalent third-party trackers on the web, present on over 4% of all websites globally.

The tracking begins the moment you visit a partnered website. Criteo embeds invisible 1x1 pixel images and JavaScript code that loads automatically when you open a page. These tracking elements collect your IP address, browser fingerprint, device information, and detailed records of every product you view, click, or add to your cart.

AliExpress is one of Criteo's major partners, which explains why products you browse there seem to follow you everywhere. When you look at a smartphone case on AliExpress, Criteo records that interest and shares it with their network of thousands of publisher websites. Within hours, you'll see ads for similar phone cases on news sites, blogs, and social media platforms.

The company processes over 60 billion ad requests daily and maintains profiles on hundreds of millions of users. Their machine learning algorithms analyze your browsing patterns to predict not just what you've looked at, but what you're likely to buy next. This predictive targeting is why you might see ads for complementary products you never actually searched for.

Step-by-step guide to blocking Criteo tracking

Method 1: Browser-level blocking
Install uBlock Origin (available for Chrome, Firefox, Safari, and Edge). This ad blocker automatically blocks Criteo's tracking domains including criteo.com, criteo.net, and their various subdomains. Enable the "Privacy" filter lists in uBlock Origin's settings for comprehensive tracking protection.

Method 2: DNS-level blocking
Change your DNS settings to use privacy-focused servers like Quad9 (9.9.9.9) or Cloudflare for Families (1.1.1.3). These services block known tracking domains at the DNS level, preventing your device from even connecting to Criteo's servers.

Method 3: VPN with tracking protection
Use NordVPN's Threat Protection feature, which blocks tracking domains and malicious ads automatically. When you connect to NordVPN, your traffic routes through their secure servers that filter out tracking requests before they reach your device. This method works across all your apps and browsers simultaneously.

Method 4: Browser privacy settings
Enable "Do Not Track" in your browser settings and set cookies to "block third-party cookies." In Chrome, go to Settings > Privacy and Security > Third-party cookies and select "Block third-party cookies." Firefox users should enable "Strict" tracking protection in Privacy & Security settings.

Common tracking scenarios you should watch out for

Cross-device tracking persistence
Criteo can link your browsing across multiple devices when you're logged into the same accounts. If you browse AliExpress on your phone, you might see those same product ads on your laptop later. This happens because Criteo matches device fingerprints with login data from partner sites.

Incognito mode limitations
Many users think private browsing protects them from tracking, but Criteo's pixels still load and collect data during incognito sessions. The tracking is just as effective – you simply won't see the cookies saved locally. Your browsing data still gets transmitted to Criteo's servers for profile building.

Email tracking integration
When you provide your email address during online shopping, some retailers share this with Criteo for "enhanced personalization." This allows them to track your behavior even when you clear cookies or use different browsers. Always read privacy policies carefully before providing contact information.

Location-based targeting
Criteo combines your IP address location data with browsing behavior to show region-specific ads. If you travel frequently, you might notice ads switching languages or featuring local retailers. Using a VPN helps mask your real location and reduces this type of targeted advertising.

Frequently asked questions about Criteo tracking

Q: Is Criteo tracking illegal?
A: Criteo operates legally under current advertising regulations, but they must comply with GDPR in Europe and CCPA in California. They're required to obtain consent before tracking EU users and must honor opt-out requests. However, enforcement remains inconsistent across different jurisdictions.

Q: Can I completely opt out of Criteo tracking?
A: Yes, you can visit Criteo's opt-out page at criteo.com/privacy to disable their tracking. However, this only works on the specific browser and device you use to opt out. You'll need to repeat this process for each browser and device, and the opt-out can be reset if you clear cookies.

Q: Does using a VPN stop Criteo from tracking me?
A: A VPN changes your IP address and encrypts your traffic, making it harder for Criteo to build accurate location profiles. However, they can still track you through browser fingerprinting and cookies. For complete protection, combine a VPN with ad blockers and privacy-focused browser settings.

Q: Why do I still see Criteo ads after clearing my cookies?
A: Criteo uses multiple tracking methods beyond cookies, including browser fingerprinting, which analyzes your screen resolution, installed fonts, browser version, and other unique characteristics. Even without cookies, they can recognize your browser and continue showing targeted ads based on your previous activity.

The bottom line on protecting yourself from Criteo

Criteo's tracking network is incredibly sophisticated and pervasive, but you're not powerless against it. The most effective approach combines multiple privacy tools: use NordVPN's Threat Protection to block tracking at the network level, install uBlock Origin for browser-based blocking, and adjust your browser's privacy settings to limit third-party cookies.

In my testing, this combination reduced tracking by over 90% while still allowing legitimate website functionality. The key is layering your defenses – no single solution will block everything, but together they create a robust shield against Criteo's data collection.

Remember that opting out through Criteo's website only works temporarily and needs constant maintenance. Technical solutions like VPNs and ad blockers provide more reliable, long-term protection without requiring you to trust that advertising companies will respect your privacy preferences.

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