A client-server system for downloading a data file from a server to a client with real time verification. The system including a server. The server including a data file, and a verification file. The verification file containing first error detection data associated with the data file. The system also including a client which communicates with the server through a network. The client including a download manager for downloading the data file from the server to the client. When the download manager downloads at least a portion of the data file, the download manager generates second error detection data associated with the data file and compares the first and second error detection data to determine if errors occurred in the data file.