Summary: Phylogenetic trees are widely used to represent the evolution of gene families. As the history of gene families can be complex (including lots of gene duplications), its visualisation can become a difficult task. A good/accurate visualisation of phylogenetic trees - especially on the web - allows easier understanding and interpretation of trees to help to reveal the mechanisms that shape the evolution of a specific set of gene/species. Here, I present treeWidget, a modular BioJS component to visualise phylogenetic trees on the web. Through its modularity, treeWidget can be easily customized to allow the display of sequence information, e.g. protein domains and alignment conservation patterns.Availability: http://github.com/biojs/biojs; http://dx.doi.org/10.5281/zenodo.7707