How do you program a key for a 2007 Mazda 3?

To program a key for a 2007 Mazda 3, you'll need a working key and the new key you want to program. Insert the working key into the ignition and turn it to the "On" position without starting the engine, then turn it back to "Off." Remove the key and insert the new key, turning it to the "On" position within 5 seconds. The security light should blink, indicating successful programming; if not, repeat the process.