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SwiftKey is one of the most popular paid Android apps of all time for Android, but that partially changes today. The well-designed predictive keyboard app used to cost $3.99, but it's now completely free. Instead of charging you up front to get the app, SwiftKey is trying out the freemium route, where you pay for add-ons and other extras.

If you already paid for SwiftKey, don't despair. As a thank-you to its customers, the company is giving you a package of themes for free, that it says is worth $5.

If you don't already know, SwiftKey is a robust keyboard app that learns your typing style and particular vernacular to offer suggestions while you type on your Android phone or tablet. It's been around since 2010 and has gained a massive following in the Android community.

This latest update ushers in a few sweeping changes, but the most significant is the new the new SwiftKey store, where you can purchase up to 30 new themes that change the color and design of your keyboard. SwiftKey already includes 14 themes in the app, but you'll now need pay a buck or two to purchase new ones. Individual themes cost 99 cents each, and you can buy packs of five for $2.99.

Screenshot by Sarah Mitroff/CNET

The update also adds an optional number row at the top of the keyboard that you can toggle on or off, predictions for emoji (in Android versions 4.1 and newer only), support for Belarusian, Mongolian, Tatar, Uzbek, and Welsh, and improved gesture trails when you use the swipe-based Flow feature.

With the updated app, SwiftKey is making a push to pull in revenue in new places. The company knows that in the long run, offering up its app for free and then charging for themes can give them a more sustainable cash flow. It's also a strategy to get more people to just start using SwiftKey, now that there's a lower barrier to entry. The hope is that more people, especially in developing smartphone markets, will want to download the app now that it's free. You can download SwiftKey for free today in the Google Play store.