Most working engineers view machine-checked mathematical proofs as an academic curiosity, if they have ever heard of the concept at all. In contrast, activities like testing, debugging, and code review are accepted as essential. They are woven into the lives of nearly all developers. In this talk, I will explain how I see machine-checked proofs enabling new everyday activities for developers of computer software and hardware. These activities have the potential to lower development effort dramatically, at the same time as they increase our assurance that systems behave correctly and securely. I will give a cosmological overview of this field, answering the FAQs that seem to stand in the way of practicality; and I will illustrate the principles with examples from projects that you can clone from GitHub today, covering the computing stack from digital hardware design to cryptographic software and applications.