What Is a Supercookie (and Why Should You Care?)

Regular cookies are like the crumbs left behind after a snack; supercookies are the equivalent of a chocolate chip trail that follows you everywhere, no matter how much you clean up. These stealthy trackers are harder to delete and way more invasive.

What Is a Supercookie?

Supercookies are advanced tracking tools that operate beyond the scope of your browser. Unlike standard cookies that sit quietly in your browser’s storage, supercookies can embed themselves into your internet service provider’s (ISP) network or your device’s metadata. This allows them to track your browsing activity persistently—even if you clear your cookies or use incognito mode.

Companies like Verizon have used them to add distinctive tracking identifiers to web traffic, enabling advertisers to follow users across the internet.

How Do Supercookies Work?

The power of a supercookie lies in its persistence. These trackers assign a distinctive identifier to your online activity, which ISPs can insert at the network level or embed in HTTP headers. Because they don’t rely on browser storage, clearing cookies or switching browsers won’t remove them.

For example, Verizon’s “unique identifier headers” (UIDHs) injected tracking codes directly into web traffic. This allowed advertisers to monitor users without relying on traditional browser cookies, making supercookies much harder to block.

Why Are Supercookies Controversial?

Supercookies are a privacy nightmare for a few big reasons:

• They’re incredibly invasive. Supercookies track you across devices, sessions, and websites, building a detailed profile of your online activity.
• They’re hard to detect or remove. Most users don’t even know supercookies exist, let alone how to get rid of them.
• They raise legal and ethical concerns. Deploying supercookies without user consent has sparked regulatory backlash, with some companies being fined for their use.

Verizon, for instance, faced a $1.35 million fine from the FCC in 2016 for using supercookies without informing users or offering a way to opt out. The controversy shows just how secretive and invasive these trackers can be.

Can You Protect Yourself Against Supercookies?

Unfortunately, supercookies are much harder to block than regular cookies. There are steps you can take to limit their reach:

• Use a VPN. A VPN encrypts your internet traffic, making it harder for ISPs to inject tracking codes into your data.
• Switch to privacy-focused browsers. Browsers like Firefox and Brave include built-in tools to block trackers and improve privacy.
• Enable DNS over HTTPS (DoH). This feature encrypts your DNS requests, making it more difficult for ISPs to monitor your web traffic.
• Use privacy-focused browser extensions, like Privacy Badger, can help block tracking attempts.

While these measures can reduce your exposure to tracking, it’s important to note that supercookies are designed to operate beyond the reach of most traditional privacy tools.

The Future of Supercookies and Privacy

Supercookies are a testament to how determined companies are to track user behavior. As traditional cookies face stricter regulations and increased scrutiny, tracking technologies are evolving to circumvent privacy tools.

For instance, browser fingerprinting and device telemetry tracking methods are becoming more common as companies seek alternatives to cookies. Privacy-focused legislation, such as GDPR in Europe, has started curbing these practices, but enforcement and oversight vary globally.

Fortunately, privacy advocates and developers are fighting back with new features like encrypted DNS and enhanced anti-tracking measures. However, the arms race between trackers and privacy tools isn’t slowing down anytime soon.

Supercookies are more than just an evolution of regular cookies—they’re a sophisticated way to monitor your online activity. These trackers operate on a deeper level, making them difficult to detect or remove.

While no solution is perfect, using tools like VPNs, secure browsers, and privacy extensions can help you regain some control over your digital footprint. Staying informed is your best defense in the ongoing battle for online privacy. Ultimately, awareness is your strongest defense—knowing how these trackers work and staying informed about emerging privacy tools can help protect your online activity.