iPhone 5S is one of the last truly small smartphones. Despite discontinuing the iPhone 5S/SE form factor, the company gave iPhone 5S users a glorious gift: iOS 12.
In the past, if you had an old iPhone, updating to the latest operating system was a bit of a gamble. Software bugs might pop up or performance might slow down. But iOS 12 does the opposite. It's not a glitzy feature-packed update. Instead, it does a lot of behind-the-scenes housekeeping that actually makes the iPhone 5S faster. It's a welcomed update and I definitely recommend downloading it.
In 2013, the iPhone 5S launched with the A7 chip, the first 64-bit processor in any smartphone. Though it's 5 years old, that same processor allows the phone to run Apple's newest OS.
Even when iOS 12 was still in beta, we noticed improvements in speed, especially when it came to opening apps like Safari and Instagram. For example, if I wrote an iMessage in iOS 11, the keyboard took its time to appear. But in iOS 12, it takes about half a second less. Most of these speed improvements are fractions of a second. But like Richard Pryor's penny-shaving scheme in Superman 3, those fractions add up.
I should note that I didn't see huge improvements across all apps. Facebook, Maps and Weather showed little to no noticeable speed boosts. But unlike previous major iOS updates, the iPhone 5S never felt bogged down.
There are a bunch of new features in iOS 12 available for younger iPhones, but some are left off from the 5S. You won't find Animoji, Memoji, AR app support, the Measure app or Message photo filters.
However, I did gain pretty much everything else including new Don't Disturb options in Control Center and Screen Time to view how much I used my phone and apps.
You can check on Cnet for the more detailed review about iPhone 5s runs iOS 12.