<p>One of the popular ways to clutter reduction techniques is to combine neighboring points into one marker that somehow shows that it contains multiple entities – this way is called clustering. In this paper, we present a JavaScript library to define optimal size of clusters and render them. Moreover, markers have to present heterogeneous data inside of clusters.</p><p>The presented library relies on server side clustering, no matter if is it a real-time clustering or a static bunch of hexagonal grids. For the library, a server provides the bunch of grid layers by different cell sizes – from smaller to larger. The library relies on data fetching provided by external library, such as Mapbox/Maplibre, so it can work with both GeoJSON and vector tiles. Using the HTML Canvas to render the marker allows to full customizing the marker image: manage the colors and proportions of cluster fractions and the size.</p>