This paper argues for a greater consideration of the role of register in the retention of heritage languages by
analyzing data on adolescent heritage-language speakers in Germany. The study addresses the following question: Which language
external factors have the greatest impact on heritage-language retention in the intimate vs formal registers? A questionnaire was
filled out by 202 students (age 15–17) in an urban area in Germany, who are all heritage-language speakers of 42 different
languages. The major finding of this study is that heritage-language retention is determined by different language-external
factors in each register. The fact that different models of heritage-language retention can be postulated for different language
registers emphasizes the need to describe the language competences of heritage-language speakers according to registers.