The functionality of a browser application is enhanced using a browser plug-in, which enables the browser application to access portions of a file system not otherwise accessible to the browser application. The enhanced functionality provided by the browser plug-in is used in one example by an image uploading web application. The browser application may also start a task in the background, such as a task for uploading several images, and then monitor the progress of the task even when the browser application navigates away from the page that initiated the task. The browser application may use a local web server running on the client device to perform tasks, including the rendering of images and monitoring progress of long running tasks.