As of Nov 21, 2020, air travelers to Canada must use ArriveCAN App or ArriveCAN online to submit travel & contact information, quarantine plans (unless exempted), & COVID-19 symptom self-assessments.

Those traveling by sea or land are instructed to use the ArriveCAN app as well, though it is not mandatory.

All travelers are reminded that they must report daily after entering Canada, unless exempt. Such reporting includes confirmation that travelers have arrived at their quarantine location within the allotted time frame and submit additional COVID-19 self-assessments.

Failure to report using either the ArriveCAN app or online service will result in contact from public health officials.

Source: Canada.ca