The exemption only fully applies if the home was your principal residence for every year you owned it. If you rented it out for a stretch, used part of it as a rental suite, or owned a second property at the same time, part of the gain can become taxable, and the calculation gets specific to your history.
You still need to report the sale on your tax return and designate the property as your principal residence, even when no tax is owed, since the Canada Revenue Agency requires the paperwork regardless of the exemption applying.
A long ownership period usually means real appreciation and real improvements the public record never saw, which is exactly what a hand-reviewed number accounts for. Get your hand-reviewed valuation from Joel Dyck.