  The digital age allows data collection to be done on a large scale and at low
cost. This is the case of genealogy trees, which flourish on numerous digital
platforms thanks to the collaboration of a mass of individuals wishing to trace
their origins and share them with other users. The family trees constituted in
this way contain information on the links between individuals and their
ancestors, which can be used in historical demography, and more particularly to
study migration phenomena. This article proposes to use the family trees of
238, 009 users of the Geneanet website, or 2.5 million (unique) individuals, to
study internal migration. The case of 19th century France is taken as an
example. Using the geographical coordinates of the birthplaces of individuals
born in France between 1800 and 1804 and those of their descendants, we study
migration between generations at several geographical scales. We start with a
broad scale, that of the departments, to reach a much finer one, that of the
cities. Our results are consistent with those of the literature traditionally
based on parish or civil status registers. The results show that the use of
collaborative genealogy data not only makes it possible to recover known facts
in the literature, but also to enrich them.
