High omission rates of global coarse-resolution burned area (BA) products entail significant underestimation of actual fire impacts, especially in tropical regions. Fire impacts on deforestation in sub-Saharan Africa (SSA) were analysed for 2016 and 2019 based on sentinel-2 satellite data (20 m). We found that fires are a precursor of forest loss, as burned areas had more than twice the chance to be deforested than unburned ones during the two study years. In moist tropical forest, the most vulnerable biome to fires, burning had even six times more chance to precede forest loss. For the whole SSA, fires contributed to more than 46% of total forest losses, more than twice the estimates based on two global BA products derived from the MODIS sensor (≥ 250 m). The vast majority of these losses occur in fragmented areas close to forest edge (< 320 m). We also found that medium-resolution BA detects more fires in late fire season, which tend to have higher impact on forest degradation than early season fires. High-resolution BA products are therefore needed to better assess fire and forest dynamics in tropical ecosystems.