The rise of computerization and fixed and mobile broadband has been an important factor for changes in the labor market of rich countries. However, as the world of tech rapidly evolves and even faster mobile internet emerges, there is still little evidence about the impact of current mobile technologies in developing countries. Brazil, in particular, during the last decade, has seen a remarkable increase in mobile internet access. In this dissertation, I explore this rapid expansion of 4G coverage to estimate the causal effects of fast mobile internet in formal local labor markets in Brazil. Since 4G technologies are not rolled out randomly, provision commitments in contracts between 4G national operators and Brazilian regulatory agency of telecommunications (ANATEL) work as an instrumental variable to internet presence. The average increase of mobile operators observed in sample is responsible for a reduction of 8 percent in formal employment contracts (about 40 percent of the variation in period). This reduction is explained by (i) reduced turnover and by (ii) displacement effects. Consistent with the routinization hypothesis, 4G expansion shifts labor demand away from manual and routine tasks. This, in turn, has benefited more high-skilled workers, increasing the share of college-graduates in the labor force and the average skill level index of local labor markets. Effects are driven by the extremes of the distribution of technological intensity but there are no changes in the industry-composition of labor markets. I also show suggestive evidence that mobile broadband is associated with job polarization.