A professional, licensed locksmith will be able to open most front door locks without the key. If you have the time and inclination, you can also learn do this yourself. This is called lockpicking—and when you aren’t doing it to your own property, or doing it as a licensed locksmith, it is illegal just about everywhere in the world.

If you want to do it yourself, you will need tools that may be difficult, or even illegal, to obtain. And because picking a lock looks like breaking into a house, you may draw the attention of police (or neighbors who might call the police), at which point you will have to explain that this is your property, and then hope that the officer believes you, understands the law, and that you actually are using the lockpicking tools legally. Otherwise you might need a lawyer. How large a risk this is depends a lot on your neighborhood and jurisdiction, though. Plenty of people do practice lockpicking as a hobby (there are YouTube videos on it).