An online system provides one or more forms on which users provide information to the online system. A form includes various fields configured to receive input from the user. While entering information on a form presented by a client device, the client device transmits a request for content to the online system. The request identifies the user, the field, and the input received via the field. Upon receiving the request, the online system applies a set of rules to information identified in the request and characteristics of the user. Information describing objects included in rules having criteria satisfied by the information in the request and the characteristics of the user is communicated to the client device for presentation to the user in conjunction with the form.