Opener spec sheets look alike at first. Most list a horsepower, a drive type, a noise rating, a battery backup, and a set of features. Read them in the order below, and check each line against the door you own, not the one in the photo.
Drive type
A chain drive moves the trolley with a steel chain. It is common on heavier doors and is typically louder. A belt drive uses a reinforced belt and is typically quieter, though the belt needs tension checked over time. A screw drive uses a threaded rod and has its own lubrication needs. A direct drive places the motor on the rail with no belt or chain to tension. It has fewer parts to adjust and usually runs quietly, but the ceiling mount has to carry the load.
Pick the drive type that fits the room and the door. If the opener sits over a bedroom wall, the noise line matters more than it does over a garage shop.
Door fit
Match the opener to the door weight. Ask the seller or installer what weight the unit is rated for and whether your door falls inside that range. Check the rail length against your garage depth, and the lift height against your ceiling. Check the headroom and side room the track needs.
Safety
Look for the entrapment protection your local code and the manufacturer require. That means photo eyes at the bottom of the door, a reversing action when the beam is broken, and a test you can run yourself after install. Ask whether the existing photo eyes will be reused or replaced.
Power and backup
Check the battery backup line. Ask how long the backup runs in general terms and what the unit does during an outage. Check the wall control and the keypad wiring the install requires.
Features
Smart features often depend on an app, a hub, or an account. Write down what each feature needs. Ask whether the app support is described in the manual and what happens if the app changes.
Paper
Read the warranty length, what it covers, and any install condition that must be met to keep it valid. Ask whether door parts such as springs and cables are included. Keep the paper with the model number and the serial number.
For service life and planning, the garage door opener page on this site covers the typical service life and when to plan. Use it with the spec read above: Garage Door Opener: typical service life and when to plan.