Travel to Canada now requires all visa-exempt foreign nationals who fly or transit through Canada to have an Electronic Travel Authorization (eTA).
Exceptions include U.S. citizens and travellers with a valid Canadian visa. Until September 29, 2016, travellers who do not have an eTA can board their flight as long as they have appropriate travel documents, such as a valid passport.
Entry requirements for other methods of travel (land, sea) have not changed.
The eTA can be obtained via an online application that takes a few minutes to complete and costs CAD $7. To find out if you need an eTA and to apply online, please see this link: http://www.cic.gc.ca/english/visit/eta.asp