Privacy software
Local-first, cross-layer fingerprint protection for people who need greater control over the identity their browser presents.
Browser Fingerprinting
Be less recognizable online.
Your browser reveals details that can connect your visits, even after you change your IP address. 404 Privacy builds privacy software, tests that exposure, and teaches teams how to reduce it.
- Open source
- No cloud
- Local software controls
Live browser surface This session
This is what websites can see about you at all timesThis information can be used to recognize you across sites even if you never log in.
Standby
Reading your browser's fingerprint
Browser—
Timezone—
Device—
OS—
Screen—(try zooming)
Canvas hash—
Language—
WebGL renderer—
These values combine into the browser fingerprint sites use to recognize this device.
Browse freely.
Browser fingerprinting combines signals available before a login or stored cookie. A VPN changes the public IP address, but many browser and rendering signals can remain recognizable. Private windows and different networks may change some observations without removing every link between sessions.
Your screen size, fonts, graphics hardware, audio processing, and installed languages can contribute to a repeatable browser profile without requiring a stored identifier. The strength of recognition depends on the signals, the environment, and the observations available.
What we do
404 Privacy combines local software, organizational assessments, and public research around a single problem: the signals that make people and teams recognizable online.
Assessments and consulting
Measure whether browsers, networks, and research workflows remain linkable across sessions and privacy adjustments, then turn those findings into practical mitigations.
Research and education
Original research, technical analysis, explainers, and training on surveillance infrastructure, browser identity, and digital attribution.
Profile driven privacy
Privacy with a multi-layer approach.
Privacy controls fail when they address one signal while leaving the rest of the identity stack intact. 404 Privacy builds and evaluates protections across JavaScript, HTTP, TLS, and TCP/IP rather than treating each layer in isolation.
The objective is not randomization for its own sake. It is reducing linkability without creating obvious contradictions between what the browser, connection, and network claim to be.
See the technical approachLearn about browser fingerprinting
JavaScript
Rendering, graphics, audio, navigator, screen, locale, and browser-exposed behavior.
HTTP
Headers, Client Hints, content negotiation, ordering, and request consistency.
TLS
Handshake characteristics, cipher and extension behavior, key shares, and client signatures.
TCP/IP
Lower-level packet and operating-system characteristics visible beneath the browser.
Workshops for your team
Privacy training for organizations
Help your team understand browser fingerprinting, digital tracking, and practical privacy controls. Tell us what your organization needs.
Explore workshop content & delivery options →
Please keep credentials, confidential client information, source material, and regulated data out of this public form.
Delivered by email. No mailing-list signup. Cloudflare provides spam verification. Privacy policy.
Who it's for
Built for work where exposure has consequences.
404 is for people whose browser identity can expose research, clients, sources, or staff.
Journalists
Reporting patterns leave a fingerprint trail that can connect your browser identity to investigations, sources, and your newsroom across sessions.
Legal professionals
Case research builds a recognizable browser profile that can expose repeated activity, work product focus, or client matters to the sites you're visiting.
Research organizations
Teams monitoring the same sites repeatedly become easier to identify over time, even when IP addresses and networks change between sessions.
Human rights organizations
For staff operating across borders or in hostile jurisdictions, a stable browser identity is an operational security risk, not just a privacy one.
Open source
Auditable, and verifiable.
404 Privacy is built around inspectable systems, limited data collection, and claims that can be tested. The software runs locally, the core implementation is available for review, and the audit methodology evaluates multiple independent layers before drawing conclusions about attribution risk.
Open implementation
Core 404 components are publicly inspectable and available under AGPLv3.
See the codeLocal-first processing
The software processes browsing traffic on the user's device rather than routing traffic through 404 Privacy infrastructure.
See the architectureAudit coverage
The audit evaluates 500+ browser, rendering, request, protocol, network, and behavioral signals across changed sessions and privacy contexts.
Review the methodologySelected for Hawaiʻi WAVE Cohort 2
Hawaiʻi WAVE is operated by the Pacific International Center for High Technology Research and funded by the Hawaiʻi Technology Development Corporation.
Press release
Updates
Research & technical analysis
Original investigations, technical analysis, and commentary on the systems used to identify, classify, and correlate people online.
News
ICE is Researching an AI Assistant to Interface with Billions of Records
Overregulation often leads to circumvention. This is a broad concern surrounding privacy minimums in the United States. If we continue to raise privacy standards, the worry is that companies that depend on data extraction will become more aggressive, invasive, and creative in their collection methods. This was largely the case when data aggregators and the advertising industry realized cookies were an easy signal to reject, and they began investing heavily in browser fingerprinting technology.
Company Updates
404 Privacy Selected for Hawaiʻi WAVE 2026-27 Cohort
404 Privacy has been selected for Cohort 2 of the Hawaiʻi WAVE Dual-Use Incubation Program. See the official release. Hawaiʻi WAVE is operated by the Pacific International Center for High Technology Research (PICHTR) and funded by the Hawaiʻi Technology Development Corporation (HTDC). The seven-month program supports technology companies exploring applications across commercial, government, and national-security markets. Aiming to provide companies the mentorship, customer-discovery support, m
News
LinkedIn Is Scanning Your Browser Extensions. This Is How They Use the Data.
When companies get caught doing this sort of thing, the response is almost always the same: "we're using this technology to combat fraud," or "ensure positive user experience," or "save computing resources," or some other hog wash. The simple truth, there's no reason to be collecting data that can be used to identify a user across the web if they're not signed in to your service. The harm of companies like Experian or LinkedIn being able to correlate all of your web traffic back to you is not
Choose the path that fits you.
For individuals
Protect your own browsing
Explore local-first software designed to reduce the stability of the fingerprint your browser and device expose online.
For organizations
Understand organizational exposure
Measure whether staff, devices, networks, and research workflows remain recognizable across sessions and privacy contexts.