In the coming months, Canada will introduce a new entry requirement, known as an Electronic Travel Authorization (eTA), for certain international travellers who fly to Canada. Entry requirements for other methods of travel (land, sea) will not change.
Starting on August 1, 2015, travellers will be able to apply for an eTA online. As of March 15, 2016, travellers will need an eTA before they board a flight to Canada.
eTA is a new entry requirement for visa-exempt foreign nationals travelling to Canada by air. It will allow Canada to screen travellers before they arrive. The authorization is electronically linked to your passport and is valid for five years or until your passport expires, whichever comes first. Applying for an eTA is an easy online process that will take just a few minutes. It only costs $7 Canadian. All you need is your passport, a credit card, and an email address.
The website for applications can be found here