You need an App.
For your customers.
You already learned, that iOS and Android are the platforms to satisfy and that everything else is dead.
Don’t waste time and money on platforms that have below 1% world wide market share – added together. If there are still unsatisfied Windows Phone users that are constantly asking, when your App will be launched on their OS, it would most likely be more cost efficient to just give them a high end Android or iOS smartphone.
Now iOS and Android, they have different OS versions, right?
Yes they do. You can count on a major OS release for iOS every fall. You can count on several important major and/or minor releases for Android throughout the year. And there are subsequent revision releases for important bug fixes.
Bug fixes on iOS? I thought they stand for high quality!
You wish. Welcome to the real world, iOS fanboys.
The customer’s expectation, competition and market pressure require Apple and Google to develop exciting new features very fast and seemingly with decreasing quality.
Due to the high fragmentation of Android devices and the high customization of the Android OS by manufacturers, there are a lot of older Android versions that are still actively used. The Android devices are not all provisioned with the latest OS version. The smartphone manufacturers simply don’t want to invest the effort on adjusting their customized Android OS for older devices that they most likely aren’t even selling anymore.
Here Apple has it a bit easier. Since they also deliver the hardware for their OS (or is it the other way around?) there are far less legacy iOS versions in the market. Apple also simply cuts the support for older devices at some point like Samsung and other manufacturers do. But as of writing this blogpost in midst 2017, the upcoming iOS 11 is going to be compatible with the iPhone 5s which was released in 2013. In the volatile world of smartphones four years of support is quite ok.
So, which version now should I support?
With iOS’ next version coming up, support versions 10 (current) and 11 (upcoming).
As a rule of thumb, support always the latest and next-to-last versions for iOS.
The adoption rate of the latest iOS has always been very fast. Given that a lot of fanboys can’t even wait for the stable release and directly install the first beta version, even with decreasing release quality, this high adoption rate will be maintained in future.
Then there are some skeptics who want to wait for the first test results. They update maybe a month after release or wait for the first bugfix version.
And finally there are the ones who stick to their old iPhones and cannot update. Keep in mind that these users are most likely the parents who are provided with the old phones by their offspring, so that they also can finally see the advantages of using WhatsApp and so on. Inspect carefully, if this is the target audience of your App.
With Android it is a bit more complicated. You really need to sum up the latest market share. For this, the dashboards are very helpful. Currently I suggest to support all Android version from 4.4 (KitKat) up. Even if Android Jelly Bean (4.1 - 4.3) still has a market share of close to 9%, your developers will probably tell you, that it does make sense to have KitKat as minimum version due to the technical improvements. Trust them.
This also is a good match with the iPhone 5s mentioned above. KitKat is four years old, so with Apps supporting the recommended OS version you’d have four years backwards compatibility.
Don’t stick with older version only for numbers in market share. The maintenance and testing effort can become quite big and you tend to limit your developers to old tools and platforms, which can relatively decrease their productivity.
Listen to your developers.
From marketings point of view, backwards compatibility for smartphones of the three to five years is quite ok.
Remember that you’ll never satisfy everyone.
Keep your target audience in mind. Is your App for Mr. and Mrs. Everyman or for the follow-the-hype-kid? You might consider this in your backwards compatibility and thus eventually reduce maintenance costs or consider supporting it, when the break even would be reached.