Can Tor browser users be identified through other means, such as browser fingerprinting?

1. Why fingerprinting matters: the basic mechanics

Browser fingerprinting collects browser and device signals (window size, fonts, canvas, timers, user-agent, etc.) to create a profile that can persist across visits even without cookies; a single unique attribute or unique combinations can identify or track a client ^[1]. Tor Project documentation and blog posts explain that maximizing the Tor Browser window, exposing monitor size or leaking other attributes increases the chance a visit becomes unique and thus trackable ^[2].

2. What Tor Browser does to reduce fingerprintability

Tor Browser applies multiple defenses to make users appear similar: it normalizes values, provides default fallback fonts, spoofs or standardizes some headers (user-agent), modifies high-resolution timers like performance.now, and uses first-party isolation and letterboxing to reduce variability in reported sizes ^{[2] [1]}. The Tor Project’s support pages explicitly state “Tor Browser prevents fingerprinting” as a design objective, and the browser aims for fingerprints that are non-unique and close to common web fingerprints ^{[5] [6]}.

3. How those protections can fail or be undermined

Protections are not absolute. If a user changes defaults, installs extensions, runs a nonstandard OS, maximizes the window, or combines Tor with other browsers or VPN setups, they can produce a unique fingerprint that ties activity to them across sites ^{[2] [4] [7]}. Community discussion and Q&A emphasize that tinkering with settings often creates uniqueness and that relying on the Tor Browser default configuration is safer than ad-hoc modifications ^{[4] [7]}.

4. Website and network-level fingerprinting — different threat models

There are two related risks: browser fingerprinting (application layer) and website- or traffic-fingerprinting (network layer). Tor’s routing hides IPs, but traffic-analysis and website-fingerprinting attacks that analyze traffic patterns to infer visited sites remain a research concern—recent surveys show WF attacks have grown more accurate under open-world conditions, meaning network-level deanonymization is an open challenge ^[3]. The network cannot mitigate application-layer leaks; conversely, browser hardening can’t fully block sophisticated network analysis ^{[3] [4]}.

5. What researchers and commentators warn about now

Academic surveys and security commentators warn that advances in machine learning, larger datasets, and improved feature extraction have pushed fingerprinting and website-fingerprinting accuracy upward, creating practical risks for high-threat users. The arXiv survey documents advances and open challenges in website-fingerprinting against Tor, indicating that perfect protection is not yet achieved ^[3]. Tech writers also note that fingerprinting can render VPNs or other privacy tools ineffective if the browser itself reveals identifying information ^[8].

6. Practical guidance distilled from the sources

Use Tor Browser without altering defaults, avoid maximizing or resizing the window, don’t install extra extensions or mix browsing profiles, and prefer the official Tor Browser bundle or privacy-focused live systems (e.g., Tails mentioned in community discussion) to reduce application-layer uniqueness ^{[2] [4] [7]}. For adversaries capable of traffic analysis, remember that browser hardening is only part of the defense—network-level research shows additional mitigations are needed and are an active area of work ^[3].

7. Competing perspectives and limitations in reporting

The Tor Project presents Tor Browser protections as substantial and central to its design ^{[5] [1]}. Independent researchers and commentators emphasize the remaining gaps: some changes (like HTTP header or OS-spoofing decisions) can alter risk trade-offs and spark debate in privacy communities, and academic work signals that website-fingerprinting is improving ^{[9] [10] [3]}. Available sources do not mention a definitive, universally-applicable method that can always identify Tor Browser users solely via browser fingerprinting; instead, reporting shows a spectrum of risk depending on configuration, attacker capability, and the exact fingerprinting method (not found in current reporting).

Final takeaway: Tor Browser substantially reduces fingerprintability when used as intended, but fingerprinting and traffic-analysis remain active threats—especially for users who change defaults or face powerful adversaries—and researchers continue to find and study attack vectors ^{[2] [1] [3]}.