The development of modern technologies used in the analysis of customer information allows not only for the collection of past data on buyers' preferences, but also makes it possible to analyse consumer behaviour on the Internet, online payments, social media and other real-time sources. The aim of the paper is to present the possibilities of using big data in the process of customizing the offer in the context of buyer behaviour. The paper analyses the process of collecting and processing data for the purposes of customizing the offer and identifies practical examples of using big data in the international business practice. It has been stated that the ability to meet the individual needs of buyers has become the basis of modern competitiveness. The real-time acquisition of non-structural data and the ability to analyse it are a condition of successful operation for businesses in technologically developed economies. To build market position, companies need to use big data analysis capabilities, anticipating future customer behaviour and customize not only the product but also all the components of the marketing mix.