Systems, methods, and other embodiments associated with shared error searching for web resource requests are described. A web resource request that includes one or more request strings is received and a error detection directive that identifies a first type of error to be located in a specified request string component is accessed. At least a portion of a first request string that corresponds to the specified request string component is searched, in a single pass, for the first type of error and other types of errors. Results with respect to the first error type are returned while occurrences of the first and other types of errors for are recorded for responding to subsequent error detection directives. Thus, a subsequent error detection directive for the other types of errors in the first request string component may be processed without re-searching the portion of the first request string already searched with respect to the first error detection directive.