Why we shrank web pages and posted barcodes in the library: new mobile web services at Vienna University Library (translation of the title). Contrary to traditional computers, the market for mobile end user devices (smartphones, tablets) is growing disproportionally fast and strong. Is has therefore become inevitable that libraries offer online information in a format that can be retrieved and displayed by these devices. In 2011, Vienna University Library developed a mobile web presence that attempts to fulfil user expectations of easy-to-find information and fast access times. For reasons of faster implementation and lower costs, it was decided to develop an HTML-based solution rather than a smartphone app. The mobile web pages are created by means of additional templates in the library's existing content management system (CMS). For the online catalogue, the existing Primo Mobile module was adapted. In addition to the mobile web pages, there were trials to assess access to information through quick response (QR) codes posted in the library