A computing platform may receive, from a client portal server, a request to authenticate a user to a user account a client portal. Based on identifying an activity the request, the computing platform may select a multi-device authentication method for authenticating the user. The computing platform may generate a first one-time passcode for a first registered device and a second one-time passcode for a second registered device, and may send the one-time passcodes to the registered devices. Thereafter, the computing platform may receive and validate one-time passcode input from the client portal server. Based on validating the one-time passcode input, the computing platform may generate a validation message directing the client portal server to provide the user with access to the user account, and may send the validation message to the client portal server. In some instances, different authentication methods may be selected for different activities.