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Internet filtering technologies play a critical role in shaping access to information online. Whether we are connecting to the Internet from our homes, coffee shops, libraries, or places of work, software that inspects, manages, and/or blocks our communications has become commonplace. When used at the level of large, consumer-facing Internet Service Providers (ISPs), Internet filtering technologies can have significant human rights impacts. A growing number of governments employ Internet filtering systems at this scale in order to undertake national-level censorship of the Internet. Filtered content ranges from pornography, hate speech, and speech promoting or inciting violence, to political opposition websites, news websites, websites affiliated with various religions, and everything in-between.

The growing responsibilities among network operators to filter content, either within private enterprises or on public networks, have given rise to a large and lucrative market. One industry report estimated the value of the web content filtering market at $3.8 billion USD by 2022. While network operators can manually configure their infrastructure to block specific websites or applications, the task can be time- consuming, complicated, and ineffective. Internet filtering companies provide professional services to ISPs and other clients to take care of this responsibility. Typically, Internet filtering companies dynamically categorize Internet resources and then let their clients choose pre-selected content categories or services that they wish to block. Customers can also add custom lists of their own to content that is filtered or blocked. In the hands of authoritarian regimes, such professional services can limit the ability of citizens to communicate freely and help impose opaque and unaccountable controls on the public sphere.


The Citizen Lab is an interdisciplinary laboratory based at the Munk School of Global Affairs and Public Policy, University of Toronto, focusing on research, development, and high-level strategic policy and legal engagement at the intersection of information and communication technologies, human rights, and global security.

We use a “mixed methods” approach to research that combines methods from political science, law, computer science, and area studies. Our research includes investigating digital espionage against civil society, documenting Internet filtering and other technologies and practices that impact freedom of expression online, analyzing privacy, security, and information controls of popular applications, and examining transparency and accountability mechanisms relevant to the relationship between corporations and state agencies regarding personal data and other surveillance activities.

Licensed under the Creative Commons BY-SA 4.0 (Attribution-ShareAlike licence). Electronic version first published in 2018 by the Citizen Lab. This work can be accessed through netsweeper/.