Toronto is considered to be one of the safest cities in North America, so it’s unlikely that you will run into any issues during your time there. Just undertake the usual precautions you would when visiting any city. Toronto is also relatively safe at night, and locals are generally very polite and quite helpful. Exploring the tourist attractions day or night should not be a problem.
But as with any populous city, crime isn’t completely non-existent. Take precautions to ensure that you don’t encounter any problems. Remain vigilant and keep an eye on your belongs. Avoid poorly lit streets and always trust your intuition. Lastly, never carry large quantities of cash.
Solo travellers to Toronto visiting the attractions and city centre will find a safe and welcoming environment. As with most cities there are some neighbourhoods that you should be more cautious visiting but these are not on the usual tourist areas. The public transport system is safe to use for solo travellers during the day and night but as always when travelling in a foreign city, keep your wits about you.