Techniques for providing resource sharing in a multi-principal browser are described. Resource sharing includes managing a resource for web entity by determining how to divide the resource to share among two or more web entities based at least in part on a Document Object Model (DOM)-recursive resource allocation policy or an application-specified resource allocation policy. A web entity includes a principal instance contending for the resource. The process identifies resource allocation mechanisms from each resource type based at least in part on the DOM-recursive sharing policy or the application-specified resource allocation policy along with the resource type.