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If you’ve ever suspected that your internet traffic is being intercepted, modified, or blocked, the Tor Project has released an open-source mobile tool that can help you investigate. The new Android app, ooniprobe, enables users to run a range of network tests that detect website blocking, traffic interception, and other signs of network tampering or censorship.
ooniprobe is currently available for Android devices and focuses on simple, privacy-conscious diagnostics. While the Tor Project plans to add more features over time, the initial release offers two core probing tools plus a basic speed test. These tests are designed to be straightforward for non-experts while still producing data that can help identify network interference and censorship.
Web Connectivity Test
The primary test included is called “Web Connectivity.” It attempts to access a variety of websites across several content categories—such as activism, religion, adult content, file-sharing, and LGBT-related sites—to determine whether access to those kinds of sites is being blocked or altered. These categories were chosen because they historically have been targets of censorship or surveillance in various countries.
When we ran the Web Connectivity test from the UK, most sites reported no access issues. A handful of failures were due to benign causes: some sites had permanently shut down, others redirected to a new URL, and a few loaded interstitials like pop-up advertisements that caused the test to flag them incorrectly. Those examples demonstrate how the app can surface potential problems while the researcher must interpret individual false positives.
HTTP Invalid Request Line Test
The second probe is called “HTTP Invalid Request Line.” It detects the presence of so-called “middleboxes”—network appliances or services that intercept, inspect, or modify HTTP traffic. When run on several networks, this test reported indications of tampering. However, in our checks the responses from the Tor servers were incomplete or missing in some cases, which suggests there may be transient server-side issues affecting results. That means users should cross-check any positive detections, and the Tor Project will likely refine the test behavior as the service matures.
Data Collection and OONI
By default, ooniprobe shares collected measurements with OONI, the Open Observatory of Network Interference. OONI is a crowd-sourced, research-oriented project within the Tor ecosystem that aggregates test results from around the world. Its goal is to track where and how governments, ISPs, or other intermediaries block websites, intercept traffic, or deploy censorship and surveillance systems. The aggregated data also helps researchers and advocates monitor changes in network performance and access over time.
OONI’s public datasets reveal clear regional patterns. For example, China shows extensive website blocking consistent with its widely known “Great Firewall.” In contrast, the datasets we reviewed listed no systematic blocking in the United States. In many European countries, detected blocks tend to focus on piracy and online gambling sites; France, for instance, has recorded blocking targets related to Islamic extremism. These findings align with local regulatory priorities and enforcement actions rather than uniform global censorship behavior.
Privacy, Legality, and Open Source
ooniprobe is open-source software, and the Tor Project encourages anyone to review the code. That transparency allows security-conscious users and researchers to verify exactly what the app measures and how it transmits results. At the same time, Tor emphasizes that users are responsible for ensuring the legality of running these tests in their country. In some jurisdictions, actively probing networks or collecting measurements could be restricted or carry legal risks, so users should understand local laws before using the app.
Because the app uploads measurement data to OONI by default, privacy-conscious users who prefer not to share results should consult the app settings and OONI’s documentation to decide how to proceed. The project aims to balance openness and research usefulness with options for users who need greater confidentiality.
Interpreting Results
ooniprobe is a powerful tool for spotting indicators of censorship and interception, but its findings require careful interpretation. False positives can occur when websites change structure, present interstitials, or go offline. Network devices and carrier settings can also produce ambiguous results. If ooniprobe flags a problem, consider repeating the test, trying it from a different network, or comparing the output to other measurement platforms. Analysts and journalists often corroborate OONI’s public datasets with manual checks before drawing firm conclusions about intentional censorship.
Getting Started
Installation and use are straightforward for most Android users. The app’s interface walks you through the available tests and explains what each measurement attempts to detect. If you choose to contribute data to OONI, your anonymous measurements will help build a larger picture of global internet interference and support research into censorship circumvention and network integrity.
ooniprobe provides a practical way to discover and document possible interference on your network, whether your concern is targeted website blocking or more subtle traffic manipulation. As the Tor Project and OONI continue to develop and refine these tools, they can become increasingly useful resources for researchers, journalists, and everyday users who want to verify the integrity of their internet connections.
Have you discovered anything noteworthy with ooniprobe? Let us know in the comments.