The theme of this master thesis is micro copy in graphic user interfaces and the effect of micro copy on user experience. The term micro copy refers to words, phrases and sentences that are a part of a user interface of a digital product (software, application, web site) that directly concern the actions that the user takes when using the product. Micro copy motivates the user to take action, helps him while the action is in progress, and gives feedback after the action was performed. Through micro copy an application or web site „communicates“ with the user, presumes his potential questions and through short and useful sentences tries to answer those questions in advance, in places where it is necessary, and builds the user's trust towards the web site and the brand that presents itself through it. It helps brands to accentuate their personality and differentiate themselves, and their web pages, from the competition. The theoretical part of the thesis focuses on defining the term micro copy, defining the elements of the interface that fall in the category of micro copy, and demonstrating existing examples. It focuses on the effect of micro copy on user experience and describes the principles and rules of writing quality micro copy. The experimental part of the thesis focusus on the comparison of two versions of a user experience that are different in terms of the micro copy. One version has generic micro copy, while the other has a quality micro copy that „communicates“ with the users, expresses the personality of the brand and builds trust.