Online CASE CPI is an example of using Big data in public statistics. In principle, it is a consumer price index based entirely on online prices: a combination of Central Statistical Office of Poland’s methodology and online data sets. An innovative method of data collection – data scrapping – allowed us to substantially reduce a time delay between data collection and a publication of results. A short, nine-month period of data collection has not given rise to make important conclusions, hence the aims of this paper are: to discuss a general framework of measuring consumer inflation online, to present preliminary results for Poland and to highlight the strengths and weaknesses of this approach. Finally, we believe that online consumer price indices have a complementary nature to conventional inflation measurement, but it might be a serious alternative, having in mind a huge growth potential of e-commerce in coming years.