This disclosure generally relates to assigning and simultaneously running multiple client-side experiments on client devices. A file includes information regarding experiments that are available, including information regarding “layers,” which are logical, imaginary containers in which each experiment “resides.” Each experiment is associated with one layer. For each experiment, the file includes information regarding a location and size of the experiment within the layer. When the client device takes an action, a software module identifies a value of an identifier associated with the action. Each such identifier is associated with one or more of the layers. The software module can calculate, for each of the associated layers, a location within the layer based on the identifier value. The computer software module can identify, based on the information in the file, each experiment that overlaps with the calculated location within each layer and cause each identified experiment to be activated.