Log files generated by the tested application during usability study contains valuable information about the user interaction but they are hard to analyze in its raw format, e.g. as a text file. Therefore it is necessary to present such a data in more suitable form. One of such form is visualization of the data, which allows analysis of
data from multiple sources simultaneously. It can better show user behavior dynamics or it allows better comparison between individual users (e.g. comparison of data of the same type but for two and more users). Interactivity is a key factor for qualitative usability analysis. There is a need for replay of audio/video recording and interactive browsing of other data collected as log files. During the qualitative study we are trying to get deeper knowledge of usability problems. It is necessary to mark spots of usability problems in the audio/video recording, to add annotations of observers or usability experts to the audio/video recording and add new interconnections between data sources.