Censys – Public Host & Network Search Engine

Censys is a public host & network search engine that allows computer scientists to ask questions about the devices and networks that compose the Internet. Driven by Internet-wide scanning, Censys lets researchers find specific hosts and create aggregate reports on how devices, websites, and certificates are configured and deployed.

Censys collects data on hosts and websites through daily ZMap and ZGrab scans of the IPv4 address space, in turn maintaining a database of how hosts and websites are configured. Researchers can interact with this data through a search interface, report builder, and SQL engine.


Censys maintains three datasets through daily ZMap scans of the Internet and by synchronizing with public certificate transparency logs:

  • Hosts on the Public IPv4 Address Space
  • Websites in the Alexa Top Million Domains
  • X.509 Certificates

You can search for records that meet certain criteria (e.g., IPv4 hosts in Germany manufactured by Siemens, or browser trusted certificates for github.com), generate reports on how websites are configured (e.g., what cipher suites are chosen by popular websites?), and track how networks have patched over time.

How to use Censys

Simple Search

If you simply search for a word or phrase, Censys will return any records that contain the phrase. For example, searching for nginx will return any records that contain the word nginx. Searching for will return all hosts in that network.

Advanced Search

Censys data is structured and supports more advanced queries including searching specific fields, specifying ranges of values, and boolean logic. For example, you can search for hosts with the HTTP Server Header “Apache” in Germany by running the query 80.http.get.headers.server: Apache and location.country_code: DE.

SQL Interface

To facilitate complex questions that can’t be expressed in a single search, we also allow researchers to run SQL queries against the raw datasets and historical snapshots.

You can access Censys here: https://www.censys.io/

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