Haptics are a way of giving additional feedback to users. For example when a contest is entered playing a “success” haptic gives the user an extra piece of feedback. The use of haptics can also be used to draw a user’s attention, for example “warning” haptics can be played to ensure that the user doesn’t miss an error message.
There should be a clear reason for the haptic to be played, and the UI should reflect that, playing a haptic without a visual indicator will cause confusion.
It’s also worth cautioning use of haptics, overusing haptic feedback can be frustrating for users. For example playing a haptic whenever a selection is made, or a button is pressed, or a screen navigation occurs would be excessive.
For most situations the platform’s stock haptic pattern should be used, Apple’s guidelines are clear and used across the eco-system. Android’s guidelines around haptics are less consistently applied, and device support is less clear however should still be used as the definition on haptics.
It’s up to each product’s UX & Design team to decide when and where to add haptics according to their own requirements.
On both iOS and Android haptics can be disabled system wide, our usage of haptics must obey this setting.