Open Observatory of Network Interference

OONI was created to make internet interference observable through measurements collected from many locations rather than through isolated reports. The project emerged from the Tor Project community and developed into an independent research initiative within the Software Freedom Conservancy ecosystem.¹ Its central concern is the difference between ordinary connectivity failure and deliberate interference, a distinction that can be difficult to establish from a single user's experience.

OONI's approach treats censorship measurement as a reproducible empirical problem. Volunteers run OONI Probe, while researchers, journalists, and civil-society groups analyze the resulting network observations. The project does not declare that a country has censored a resource solely because a test failed; measurements are interpreted alongside control connections, historical patterns, local conditions, and other evidence.

OONI Probe runs specialized tests that compare expected network behavior with observed behavior. Website testing can reveal DNS anomalies, connection failures, HTTP blocking pages, and interference in TLS connections; other tests examine messaging applications, circumvention tools, and middleboxes that alter traffic.²

The software records technical metadata such as measurement time, network provider, tested input, and response characteristics. It is designed to avoid collecting the content of private communications, although measurements can still carry privacy risks because network metadata and tested URLs may be sensitive. OONI therefore documents its data practices and encourages users to understand the risks before running tests.

Results are published through the OONI Explorer and related APIs in formats intended for independent analysis. Researchers can compare observations across networks and dates, identify blocking events, and inspect raw or summarized network evidence rather than relying only on a headline classification.

OONI's public measurements support research into website blocking, application interference, shutdowns, and the technical infrastructure of censorship. Journalists have used the data to investigate disruptions, while researchers use it to study regional patterns and changes over time.³ The data can also help network operators distinguish policy-based filtering from routing failures, service outages, or configuration errors.

Interpretation requires caution because a measurement is an observation, not automatically proof of government responsibility. A blocked URL may reflect a private network policy, a faulty resolver, geolocation behavior, or an unavailable server. OONI's analysis commonly combines its results with independent reports, legal context, routing data, and local technical knowledge. This layered method is especially important where networks are unstable or where censorship mechanisms vary by provider.

OONI's less visible contribution is its attempt to standardize censorship evidence across highly different networks. Its test lists include both globally significant services and locally relevant websites, allowing measurement priorities to reflect conditions in particular countries rather than assuming that a universal list is sufficient.²

The project also documents interference techniques that are subtler than a simple block page. These include DNS tampering, endpoint throttling, transparent proxies, injected responses, and manipulation of encrypted-connection handshakes. In some cases, interference is intermittent or provider-specific, so repeated testing can reveal patterns that a one-time check misses.

Because anyone can contribute measurements, OONI illustrates both the strength and limitation of volunteer sensing: broad geographic reach is possible, but coverage is uneven and participation may be dangerous in restrictive environments. Its findings are therefore most useful when their collection context, uncertainty, and safety implications remain visible.

Network interference

A technical change or disruption affecting communication over a network, including blocking, tampering, throttling, or redirection.

OONI Probe

The open-source application used to run OONI's network measurement tests.

Middlebox

A device or service positioned between endpoints that can inspect, filter, redirect, or modify network traffic.

DNS tampering

Interference with domain-name lookups that can return false results, prevent resolution, or redirect users.