Square announced Wednesday the launch of a software development kit that allows merchants to process payments on Square inside their mobile app.

The San Francisco-based firm said the SDK will let developers write a few lines of code and add square to their iOS or Android apps, which are available in the U.S., U.K., Australia, Canada and Japan, according to a press release. The SDK is also available on Flutter.

Square said the kit makes it the only platform with first-party products that provide for in-person, web and mobile app transactions

"With the introduction of in-app mobile payments to the Square platform, developers now have a complete, omnichannel payments solution for all their payments needs," Carl Perry, developer lead at Square, said in the release.

Buyers can use credit or debit cards for purchases or use digital wallets like Apple Pay and Google Pay, according to Square.

Among the companies that beta-tested the SDK was PepperHQ, which creates merchant branded mobile apps for hospitality companies and Brushfire, a ticketing and registration platform. Brushfire officials said the SDK increased conversion rates by 20 percent.