# Encore: Lightweight Measurement of Web Censorship with Cross-Origin Requests

arXiv: https://arxiv.org/abs/1410.1211 · HTML: https://mlsanity.com/paper/1410.1211/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 5 Oct 2014.

## Built on by (most cited first, 1 of 1)

- [Institutionalising Ethics in AI through Broader Impact Requirements](https://mlsanity.com/paper/2106.11039/) (2021)

## Abstract (arXiv)

Despite the pervasiveness of Internet censorship, we have scant data on its extent, mechanisms, and evolution. Measuring censorship is challenging: it requires continual measurement of reachability to many target sites from diverse vantage points. Amassing suitable vantage points for longitudinal measurement is difficult; existing systems have achieved only small, short-lived deployments. We observe, however, that most Internet users access content via Web browsers, and the very nature of Web site design allows browsers to make requests to domains with different origins than the main Web page. We present Encore, a system that harnesses cross-origin requests to measure Web filtering from a diverse set of vantage points without requiring users to install custom software, enabling longitudinal measurements from many vantage points. We explain how Encore induces Web clients to perform cross-origin requests that measure Web filtering, design a distributed platform for scheduling and collecting these measurements, show the feasibility of a global-scale deployment with a pilot study and an analysis of potentially censored Web content, identify several cases of filtering in six months of measurements, and discuss ethical concerns that would arise with widespread deployment.