It is important to keep your Will in a safe place which is accessible to your executor. If your Will can't be located after you've died, it's basically as if you've died without a Will.
Keeping your Will at home
The simplest option is to just keep your Will at your home with your important documents and tell your executor where it is. If you die, your Will can easily be found.
It is possible that the Will can be accidentally destroyed, such as in a fire. This risk can be mitigated by storing the Will using a fireproof safe or filing cabinet. In addition, where a Will was accidentally destroyed, it is possible for a copy of the Will will be accepted by the court.
Having your lawyer keep your Will
Some people choose to keep their Will with the lawyer who drafted it for them. This helps ensure safekeeping, but it can make it more difficult to locate your Will. Your executor will need to keep your lawyer's name and contact information, but lawyers move and retire while law firms change names, move and close.
Storing a Will in a safety deposit box
Some people choose to keep their Will in a safety deposit box in a bank. Your Will be secure, but you will need to ensure your executor will be able to access the safety deposit box (and this may be challenging if the safety deposit box is not held jointly with the executor).
Depositing Will with court
In Ontario, a Will can also be deposited with the court. In general, the only people who can deposit a Will with the court are you, a person authorized by you in writing or a lawyer who was holding your Will when they retired. While you are living, the only people who can retrieve a Will from the court are you or your guardian for property.
After your death, your executor or their lawyer can retrieve a copy of the Will. Also note that, after your death, any person can inspect and copy your Will if it is with the court by written request containing your date of birth and proof of death.