How do you unlock a washing machine door mid cycle?

Generally, you can open a front-load washing machine if it's been running for less than five minutes by pressing the Start/Pause button. The machine will assess whether or not it's safe to do so — by checking the water level and temperature. If both are good, then the door should unlock. However, if your washer is in the middle of its cycle, check your manual as some machines have an emergency drain feature that'll let you stop and drain everything while also unlocking the door; though using this option could damage your machine, so only use it as a last resort.