- Power source: Many dash cams are powered by the cigarette lighter socket in your car, though there are some that have the ability to be hard-wired directly to your battery. The latter requires professional installation outside the scope of this guide, so we're focusing on the more typical DIY-friendly models here. In addition, some models contain a lithium-ion battery—like your phone—while others contain a capacitor to store energy. If you live in a particularly hot climate, you'll want a capacitor model, since they're more heat resistant than their battery-powered siblings.
- Field of view: Ideally, you want a dash cam with as wide a field of view as possible, so it can see cars not just in front of you, but to the sides, too. You'll find 140 to 160 degrees is fairly common, though there are some models that go as wide as 170 degrees.
- Picture quality and frame rate: The sharper the video captured by your dash cam, the better, so you can make out the license plate numbers of other cars on the road. Resolution is part of this equation, but not all of it—you also need to consider picture quality in low light, for example, so you can get good nighttime footage. The best thing you can do is look at reviews and see if you can find footage online taken from the model you're researching.
- Number of cameras: At the bare minimum, a dash cam will record video from your front windshield. But some models have other cameras for other views, like one for your back windshield or a camera facing the driver's seat to capture other people in the car. (This is particularly useful for Uber and Lyft drivers who want evidence of anything that happens on the job.)
- Built-in screens and GPS: While it's not required, some models have screens on the back of the camera that allows you to see the video it's recording—which can be helpful during the initial setup, if nothing else. Others have built-in GPS or support for separate GPS modules, so you can attach your location to the footage you capture. Some may even offer turn-by-turn navigation (though honestly, the navigation on your phone is probably better).
- Wi-Fi and app support: Dash cams with built-in Wi-Fi allow you to view and share footage from an app on your phone, rather than having to remove the SD card and insert it into a computer. Again, this isn't imperative, but some people may find it useful.
- Emergency sensors: Your dash cam is limited by the amount of space on its SD card, and when its storage is full, it'll automatically erase old footage to make room for new footage. I highly recommend getting a dash cam that can detect when you've been in a collision, since it allows the dash cam to "lock" that footage from being overwritten as you continue driving. If your dash cam is wired directly to your car (rather than plugged into the cigarette lighter), it may also have the ability to record collisions that happen while you're parked, which is a nice perk.