Are web browsers ready to handle a larger portion of the processing load in our GIS applications? Web-based GIS and mapping applications are traditionally based on a client-server model, where most of the data processing work is placed on the server. This study examines what happens when that processing load is shifted to the client, using JavaScript to process geospatial data with GIS operations directly in the browser.The time needed to complete common GIS tasks using the JavaScript library JSTS Topology Suite were benchmarked in popular web browsers including Chrome, Firefox, Internet Explorer, Opera, and Safari. The GIS operations buffer, union, and Voronoi diagram were tested with a suite of points, lines, and polygons ranging in size from 10 up to 100,000 vertices. The testing platforms included Windows, Mac, and Linux desktops and laptops.The same geoprocessing tests were conducted on a cloud-based Linux server using the Java library JTS Topology Suite as a performance comparison of server-side processing applications. The various testing configurations were then analyzed to see how browsers stack up to the performance of traditional client-server applications.