Evercookie: A Persistent Tracking Mechanism
Evercookie is a JavaScript technique that creates persistent identifiers in a browser. This article explains how Evercookie works, its value for tracking users, its limits, and what users can do to protect themselves.
What is an Evercookie?
An Evercookie is a tracking method that writes the same value to multiple storage mechanisms in a user’s browser. Unlike regular cookies, Evercookies are difficult to remove and can restore themselves after deletion.
How Does Evercookie Work?
- Storing Data in Multiple Places: Evercookie writes the same value to several browser storage options, including standard HTTP cookies, Local Shared Objects, and HTML5 storage.
- Rebuilding Mechanism: If one location is cleared, Evercookie reads the remaining copies to recreate the missing ones.
- Persistent Tracking: This redundancy and rebuilding logic enable long-term user tracking.
Value of Evercookie for Tracking
Evercookie supports tracking because of its:
- Persistence: Copies can remain after deletion attempts.
- Cross-Session Tracking: It can link activity across multiple browsing sessions.
- Resistance to Blocking: Traditional cookie blockers may not cover all storage paths Evercookie uses.
Limitations of Evercookie
- Privacy Concerns: Its persistence can be invasive.
- Regulatory Restrictions: Some jurisdictions restrict or regulate persistent tracking technologies.
- Browser Support: Not all browsers expose every storage mechanism Evercookie relies on.
Protecting Against Evercookie
You can reduce exposure to Evercookie by:
- Using Privacy-focused Browsers: Tor or browsers with strict privacy settings can reduce these traces.
- Disabling Flash and Other Plugins: Disable plugins that expose additional storage vectors.
- Regularly Clearing Browser Data: Clear cookies and other storage mechanisms on a regular schedule.
Conclusion
Evercookie enables persistent tracking and creates real privacy risks. Understanding how it works, and applying protective measures, helps you keep control of your browsing data and privacy.
Frequently asked questions
What is an Evercookie?
An Evercookie is a JavaScript tracking technique that stores the same value in multiple storage mechanisms in a user’s browser. Unlike a regular cookie, an Evercookie can be difficult to remove because copies in other locations may recreate the data after one location is cleared.
How does Evercookie restore data after deletion?
Evercookie restores deleted data by reading copies of the same value from browser storage locations that remain after one location is cleared. The technique then recreates the missing copy, so the identifier can persist across browsing sessions.
How can I protect against Evercookie?
You can reduce exposure to Evercookie by using Tor or a browser with strict privacy settings. Disabling Flash and other plugins can reduce additional storage vectors, and regularly clearing cookies and other browser storage mechanisms can help remove stored copies.
