The iPhone 5s was the first Apple product to include the Touch ID fingerprint sensor. Apple introduced the feature in September 2013, placing the sensor beneath a redesigned Home button.
Touch ID allowed users to unlock the phone and authenticate App Store and iTunes purchases with a fingerprint. The sensor used capacitive scanning and a stainless-steel detection ring, while fingerprint data was stored locally in the iPhone 5s's Secure Enclave rather than uploaded to Apple's servers.
Apple's 2012 acquisition of AuthenTec helped provide the technology behind the system. Touch ID later expanded to products such as the iPad Air 2 and iPhone 6. The iPhone 5c was released alongside the 5s but retained the traditional Home button, making it an easy wrong answer.