What is this site?
It tests whether individual web addresses can be reached from inside mainland China, and has done so without a break since 2011. Every page here is built from those measurements: the verdict for one URL, the evidence behind it, and how it has changed over the years. Nothing is crowdsourced or reported from your browser — probes inside mainland China and a control probe outside fetch the same address at the same moment, and the difference between them is the finding.