Although the charmonium spectrum seems to be well investigated, charmonia can still be used as benchmarks to test our QCD predictions, as these states lay in the transition region between perturbative and non-perturbative QCD. Despite the need for experimental confirmations, setbacks arise from limited statistics because of the production processes of all non-vector states. The properties and many decay channels of some charmonium states (such as hc, χcJ, or ηc(2S)) are still far from being known. Since 2009, BESIII has been scanning and investigating the charmonium region to shed light on open questions. Thanks to its unique J/ψ and ψ(2S) datasets, BESIII could overcome statistical limitations. Recent results on charmonium decays from the BESIII Collaboration are presented.