The requirement for a TRV also applies to temporary residents who are transiting in Canada. This requirement depends on your country of residency. If you do not require a visa to enter Canada, you may require an Electronic Travel Authorization (eTA).
What is Electronic Travel Authorization?
If you are from one of the countries which do not require a TRV to visit Canada, then you might have to get an Electronic Travel Authorization (eTA). You must check if you need an eTA before arriving to Canada and apply for one.
According to the new entry requirements, visa-exempt foreign nationals who come to Canada or transit through a Canadian airport, need an eTA. U.S. citizens and people with a valid Canadian visa, Canadian citizens or permanent residents do not require an eTA. eTA requirement is only required ifflying in, visa exempt travellers do not need an eTA if they are entering Canada via land or sea.
The fee for an eTA application is CAD $7, and according to their official website, most applications are approved within minutes of applying. An eTA can be valid for about five years or earlier if your passport expires. With a valid eTA you can travel to Canada as often as you want for short stays which is normally six months at a stretch.