LONDON — Typing on the glass of a smartphone can be a headache. The keyboards are tiny. Errors are easy to make, even on the simplest of words. And autocorrect, the function meant to fix typing mistakes, often introduces errors, switching words that have little to do with what people actually mean.

Consumers’ irritation with typing has enticed the likes of Google, Apple and several start-ups to try to put the smart into smartphone keyboards — knowing that there is a big opportunity in having such a prominent place in users’ hands.

Perhaps no company, though, has found more success with enhancing keyboards than SwiftKey, a London start-up that first released a keyboard app in 2010. SwiftKey says the app, which cost $4 until last Wednesday, when it became available free, was downloaded more than 30 million times. It ranked as one of the most popular paid smartphone applications on Google’s Play Store.

The app predicts what you will type next by using artificial intelligence and reams of online data, including what you type on other apps, to learn what words you typically use. It then applies that information to predict what you will type next.