In the more populated areas of Ontario, especially southern and south-western Ontario (within a few hours drive of Toronto) access is often complicated, with many cliffs closed to climbing. The Ontario Alliance of Climbers (OAC) monitors this, and negotiates for access to cliffs, or to avoid closures. They maintain a crag status list at: https://www.ontarioallianceofclimbers.ca/crag-status/
The Ontario Ministry of Natural Resources and Forestry also maintains an online crown land use policy atlas. This can often be used to determine the ownership status of the land on which a cliff is located in Ontario. It can be found at: http://www.giscoeapp.lrc.gov.on.ca/web/MNR/NHLUPS/CLUPA/Viewer/Viewer.html .