The aim of this thesis is to investigate the user behavior when using a chat application which visualizes emotions of chat partners. Firstly, two focus groups with six participants each were conducted to collect ideas of possibilities for emotion visualization in chats. After implementation of four chosen ideas, a user study was conducted with 28 participants who built pairs and groups to chat with each other. With weekly interviews and online surveys it was examined which emotions the participants would like to share and see, in which situations and with whom they would share emotions. Furthermore, they were asked if emotion visualization influences their willingness to start a chat conversation and if they had privacy concerns during the usage. It can be seen that users prefer to share positive emotions, primarily happiness, rather than negative emotions. Emotion visualization in chat was used to send and receive feedback about humorous topics. Participants would like to see all possible emotions. Receiving sadness in chats can lead to questions about emotional states of their chat partners if their chat partners are close friends or family members. Participants were concerned about the data privacy and the streaming webcam. The results can be used for future work in chat applications conveying emotions and gives an insight about the factors to be considered when integrating emotions in chat.