Privacy Badger
Privacy Badger is a free, open-source browser extension created by the Electronic Frontier Foundation that automatically blocks hidden third-party trackers based on algorithmic detection rather than static filter lists. It sends the Global Privacy Control and Do Not Track signals and replaces social media widgets with click-to-activate placeholders to protect user privacy.
Score generated by AI agents based on publicly cited evidence and reviewed by the project maintainer. Not independently validated.
Score History
Timeline events are AI-curated from public reporting. Score trajectory is derived from documented events.
Privacy Badger launched as an alpha extension for Chrome and Firefox, built by EFF as a response to the advertising industry's refusal to honor Do Not Track. The nonprofit's 501(c)(3) structure ensured no monetization, no shareholders, and full open-source transparency from day one. Initial capabilities were basic but the core heuristic tracking detection was functional.
Privacy Badger reached 1.0 with fingerprinting detection, supercookie blocking, and integration with EFF's new Do Not Track Policy standard. Over 250,000 users had already adopted it. EFF simultaneously launched Let's Encrypt as a co-founder, demonstrating its commitment to building privacy infrastructure. The extension remained fully free and open source with no lock-in.
Privacy Badger grew past one million users and expanded to Opera with the 2.0 release. EFF launched Badger Sett to pre-train new installations with tracker data, solving the cold-start problem. The extension added Facebook link tracking protection and WebRTC leak prevention. The D1 score ticked up slightly as occasional site breakage became a documented pattern, though this reflected the tension between aggressive tracking protection and website compatibility rather than intentional degradation.
Google Security Team disclosed that Privacy Badger's local learning could be exploited for fingerprinting and limited history sniffing. EFF transparently disabled local learning by default, shifting all users to a shared pre-trained blocklist. The same update added Global Privacy Control support, which gained CCPA legal backing in January 2021. The W3C had disbanded its Do Not Track working group in 2019, making enforcement tools like Privacy Badger more important than voluntary standards.
Privacy Badger reached four million users with its largest-ever blocklist of 2,000+ domains powered by Badger Swarm distributed scanning. The extension adapted to Google's Manifest V3 constraints, added Privacy Sandbox opt-out, expanded widget replacements to newer platforms, and maintained active development with regular releases. EFF's leadership transition with Cindy Cohn's planned departure proceeded orderly. The product remains a model of healthy, nonprofit-driven software.
Alternatives
Free, open-source ad and tracker blocker with broader blocking coverage than Privacy Badger, including full ad blocking via filter lists. If you want tracker protection plus comprehensive ad blocking in one extension, uBlock Origin is the standard. Easy switch: just install it.
Commercial ad blocker with a free browser extension that combines ad blocking and tracker protection. Offers system-wide blocking on desktop and mobile via paid apps. A good option if you want Privacy Badger's tracker blocking plus full ad blocking in a single tool.
Dimensional Breakdown
Summaries below were written by AI agents based on the cited evidence. They are editorial interpretations, not independent research findings.
Dimension History
Timeline (32 events)
EFF Founded After Secret Service Raids on Steve Jackson Games
Mitch Kapor, John Perry Barlow, and John Gilmore founded the Electronic Frontier Foundation in response to the U.S. Secret Service's raid on Steve Jackson Games and broader Operation Sundevil actions. The organization was created to defend civil liberties in the emerging digital world, establishing the nonprofit that would later create Privacy Badger.
EFF Wins Steve Jackson Games v. Secret Service Landmark Case
A federal court ruled that the Secret Service's seizure of Steve Jackson Games' computers and bulletin board system violated the Privacy Protection Act. Judge Sparks awarded over $50,000 in damages, establishing the first precedent that law enforcement cannot access private electronic mail without a warrant.
Bernstein v. DOJ Establishes Code as Protected Speech
The Ninth Circuit Court of Appeals ruled in Bernstein v. Department of Justice that software source code is speech protected by the First Amendment. EFF served as lead counsel in this landmark case, which invalidated U.S. export restrictions on cryptographic software and paved the way for international e-commerce.
EFF Launches Panopticlick Browser Fingerprinting Research
EFF launched Panopticlick, a research project demonstrating that 84% of browsers have unique fingerprints. The study, presented at the Privacy Enhancing Technologies Symposium in Berlin, showed that browser configurations contain at least 18.1 bits of entropy, making tracking without cookies feasible. This research directly informed Privacy Badger's later fingerprinting detection capabilities.
Privacy Badger Alpha Released for Chrome and Firefox
EFF released the alpha version of Privacy Badger, a free browser extension that automatically detects and blocks third-party trackers using heuristic learning rather than static filter lists. The tool was created as EFF's response to the advertising industry's refusal to honor Do Not Track requests. Privacy Badger analyzed third-party domains and blocked those using uniquely identifying cookies across three or more sites.
Privacy Badger Beta Released with ShareMeNot Integration
EFF released the Privacy Badger beta for Chrome and Firefox, integrating ShareMeNot functionality developed by Franzi Roesner at the University of Washington. ShareMeNot replaced social media share buttons with click-to-activate placeholders, preventing Facebook, Twitter, and Google+ buttons from tracking users before they clicked. Over 150,000 users had already installed the alpha.
Privacy Badger 1.0 Released with Fingerprinting and Supercookie Detection
EFF released Privacy Badger 1.0 for Chrome and Firefox with new capabilities to detect canvas fingerprinting and HTML5 local storage supercookies. The release also included a new UI, translations into 4 languages, and integration with EFF's new Do Not Track Policy. Over 250,000 users had installed alpha and beta versions.
EFF Launches Do Not Track Policy Standard with Coalition
EFF launched its own Do Not Track Policy standard with a coalition including Disconnect, Adblock, Mixpanel, Medium, and DuckDuckGo. The standard required that users who enabled DNT would not be tracked without clear consent, with strict data retention limits. Privacy Badger 1.0 was integrated with this policy, unblocking domains that committed to honoring it.
Let's Encrypt Public Beta Launches with EFF as Co-Founder
Let's Encrypt launched its public beta, issuing free TLS certificates to encrypt web traffic. EFF co-founded the project alongside Mozilla, and developed Certbot, the recommended ACME client for automating certificate issuance. Over 130,000 certificates were issued in the first two weeks, demonstrating EFF's commitment to building privacy infrastructure alongside Privacy Badger.
Privacy Badger 2.0 Released with Opera Support and WebRTC Protection
Privacy Badger 2.0 launched for Chrome, Firefox, and Opera with significant improvements: support for incognito/private browsing, import/export of tracker-blocking settings, WebRTC IP address leak protection, HTML5 ping tracking blocks, and Firefox multiprocess (E10S) compatibility. The extension had approximately 900,000 daily users at the time of release.
Privacy Badger Surpasses One Million Users
EFF announced Privacy Badger had surpassed one million users across Chrome, Firefox, and Opera. The milestone represented rapid growth from the 250,000 alpha/beta users in August 2015. The extension was available in multiple languages and had become one of the most widely used privacy tools on the web.
Privacy Badger Adds Facebook Link Tracking Protection
A new Privacy Badger update added the ability to remove Facebook's link shimming, which replaced outgoing URLs with redirect links through l.facebook.com for tracking purposes. The extension detected and replaced shim URLs with their original equivalents and blocked the tracking beacon requests, protecting users from Facebook's outgoing link surveillance.
EFF Launches Badger Sett Pre-Training System
EFF released Badger Sett, an automated training system that uses Selenium to drive Privacy Badger through thousands of popular websites and record tracking behaviors. The pre-trained tracker data was bundled with new Privacy Badger installations, solving the cold-start problem where new users had no tracker knowledge. The blocklist grew from approximately 300 domains to steadily expand with each update.
W3C Disbands Do Not Track Working Group
The W3C Tracking Protection Working Group was formally disbanded, citing insufficient deployment and lack of support among user agents, third parties, and the broader ecosystem. The advertising industry had effectively ignored DNT signals. Privacy Badger continued sending DNT headers but the failure of the standard reinforced the need for enforcement tools like Privacy Badger rather than voluntary compliance.
Privacy Badger Adds Cookie Sharing Detection Heuristic
EFF released a Privacy Badger update with a new heuristic to detect first-to-third-party cookie sharing via pixel tracking. The system detected when third-party image requests contained 8+ character matches with first-party cookies, indicating cookie sharing for tracking purposes. This enabled blocking of trackers like Google Analytics that had evaded previous detection methods.
Google Security Team Discloses Fingerprinting Vulnerabilities
Google Security Team members Artur Janc, Krzysztof Kotowicz, Lukas Weichselbaum, and Roberto Clapis responsibly disclosed security issues with Privacy Badger's local learning feature to EFF. The first disclosure revealed that the cookie sharing heuristic (added July 2019) could allow attackers to extract first-party cookie values. EFF immediately removed the vulnerable heuristic.
Privacy Badger Disables Local Learning by Default
Following the Google Security Team disclosures, EFF disabled Privacy Badger's local learning by default. The second class of vulnerability showed that attackers could manipulate local learning to create unique fingerprints identifying users or perform limited history sniffing. All default users now share an identical pre-trained blocklist from Badger Sett. Users can still opt into local learning via Advanced settings. EFF stated they found no evidence the techniques were used in the wild.
Privacy Badger Adds Global Privacy Control Signal Support
Alongside the local learning change, Privacy Badger began sending the Global Privacy Control (GPC) signal to every website visited. GPC was designed as a successor to Do Not Track with legal backing under the California Consumer Privacy Act, which requires businesses to honor user-enabled global privacy controls as valid opt-out requests. EFF co-developed the GPC standard with a coalition including The New York Times, DuckDuckGo, Brave, and Mozilla.
EFF Rebrands Panopticlick as Cover Your Tracks
EFF relaunched its browser fingerprinting research tool, originally launched as Panopticlick in 2010, as Cover Your Tracks. The updated tool tested both browser uniqueness and the effectiveness of tracker blockers including Privacy Badger. The rebranding reflected a decade of evolution in fingerprinting research and browser privacy tooling.
California AG Confirms GPC Satisfies CCPA Opt-Out Requirement
California Attorney General Xavier Becerra publicly confirmed that Global Privacy Control satisfies the CCPA requirement for businesses to honor user-enabled privacy controls as valid opt-out requests. This gave legal backing to the GPC signal that Privacy Badger sends by default, meaning businesses are legally required to stop selling personal data when they receive it from Privacy Badger users in California.
Privacy Badger Adds CNAME Tracker Detection
Privacy Badger 2021.6.8 introduced detection of CNAME-cloaked trackers, where prominent tracking services like Adobe hid their tracking domains behind DNS aliases that appeared to belong to the visited website. AdGuard provided the CNAME DNS data powering this feature, enabling Privacy Badger to block a previously invisible class of tracking in Chrome and Chromium-based browsers.
Supreme Court Rejects EFF's Jewel v. NSA Surveillance Case
The U.S. Supreme Court rejected EFF's flagship NSA surveillance lawsuit, Jewel v. NSA, which had challenged the government's mass collection of Americans' phone and internet communications. The court effectively validated government claims that mass surveillance was too secret to be challenged in open court. While not directly about Privacy Badger, the rejection underscored the importance of technical privacy tools when legal challenges fail.
EFF Retires HTTPS Everywhere Extension
EFF retired its HTTPS Everywhere browser extension in January 2023, as major browsers had integrated HTTPS-only mode natively. The discontinuation reflected the project's success: HTTPS adoption had become widespread. Privacy Badger became EFF's sole actively maintained browser extension, with continued development and updates.
Privacy Badger Blocks Google Link Tracking Across Multiple Products
A Privacy Badger update removed Google's link tracking redirects across Google Docs, Gmail, Google Maps, Google Images, and dynamically loaded Google Search results. The extension blocked tracking beacon requests at the network layer using the webRequest API. EFF noted that Google's upcoming Manifest V3 would restrict this capability by replacing webRequest with the more limited Declarative Net Request API.
EFF Launches Badger Swarm for Distributed Tracker Scanning
EFF introduced Badger Swarm, a distributed cloud-based system that orchestrated parallel Privacy Badger scans across thousands of websites. The system dramatically expanded scanning capacity beyond what single Badger Sett runs could achieve. Privacy Badger's blocklist grew from under 1,200 to over 2,000 domains, and the expansion enabled a new capability: blocking fingerprinters hosted by content delivery networks.
Privacy Badger Expands Widget Replacement System
Privacy Badger added click-to-activate replacements for embedded tweets, continuing the widget replacement lineage from ShareMeNot (2012) through Flashblock (2004). The system replaced tracking widgets with privacy-preserving placeholders that users could click to load on demand. The update also improved replacements for YouTube, SoundCloud, and other embeds.
Privacy Badger Automatically Opts Users Out of Google Privacy Sandbox
Privacy Badger began automatically disabling Google's Privacy Sandbox features: Ad topics, Site-suggested ads, and Ad measurement. EFF argued that despite marketing itself as privacy-protective, Privacy Sandbox shifted tracking control from third parties to Google rather than eliminating it. Research showed that as few as three topic observations could identify 60% of users. Google announced the same day that it would not deprecate third-party cookies in Chrome.
EFF Publishes Decade-in-Review of Privacy Badger's Anti-Tracking Mission
EFF published a comprehensive article documenting Privacy Badger's decade-long evolution fighting online tracking. The piece detailed how the extension had adapted to counter new tracking methods including canvas fingerprinting, supercookies, CNAME cloaking, link shimming, and Google's Privacy Sandbox. Privacy Badger continued sending both DNT and GPC signals and blocking trackers that ignored them.
EFF Executive Director Cindy Cohn Announces Departure
Cindy Cohn announced she would step down as EFF Executive Director by mid-2026 after 25 years with the organization and a decade as its top leader. Under her leadership, EFF grew from roughly 60 to 125 staff members. The organization launched a search for her successor with Russell Reynolds Associates. Cohn's departure represents an orderly leadership transition for the nonprofit behind Privacy Badger.
EFF Promotes Privacy Badger for Libraries and Schools
EFF published guidance for system administrators on deploying Privacy Badger organization-wide in libraries, schools, and other institutions. The article cited a Human Rights Watch analysis finding 89% of EdTech products shared children's personal data with advertisers, and referenced CISA's recommendation that federal agencies deploy ad-blocking software. Four million users were using Privacy Badger at the time of publication.
Privacy Badger Adds Bluesky, Instagram, and Threads Widget Replacements
Privacy Badger added click-to-activate widget replacements for Bluesky, Instagram, and Threads embeds, expanding its privacy-preserving placeholder system to cover newer social media platforms. The update also improved existing replacements for Spotify, SoundCloud, Twitch, and YouTube embeds, reflecting continued active development.
Privacy Badger 2026.2.20 Fixes Chrome Cookieblocking Bug
Privacy Badger released version 2026.2.20 fixing a bug where cookieblocking (domain toggle set to yellow) was not working in Chrome, Edge, and Opera. The update also improved translations for Arabic, Traditional Chinese, German, Japanese, and Portuguese, and fixed blocking of known CNAME aliases in Chrome. This represented continued maintenance under Manifest V3 constraints.