Some applications are required to display a large number of locations or markers. Google Maps mashups can suffer performance problems when trying to display a large number of markers at any one time. To overcome this poor performance, the information displayed on the map needs to be simplified, for example, by using some kind of clustering.

Clustering is the process of grouping closely-positioned locations together and representing them with a single pushpin. When you zoom in, those locations will become further apart and separate into their own pushpins.

The client-side part of “Client Side Clustering” clusters data on the fly in JavaScript rather than going back to the server to request more data. When you have a few thousand locations to display on the map, client side clustering can be significantly faster than server side clustering and also cuts down on requests to your server, thus making your application more scalable.