Mozilla wants to introduce a common web API (application programming interface) to make payments easy and secure on Firefox OS devices. As a first step, Mozilla will introduce navigator.mozPay() in Firefox OS so that web apps can accept payments. According to Kumar McMillan, who works on Firefox OS and the Firefox Marketplace, navigator.mozPay() is a JavaScript API inspired by Google.payments.inapp.buy() but modified for things like multiple payment providers and carrier billing. When a web app invokes navigator.mozPay() in Firefox OS, the device shows a secure window with a concise UI. After authenticating, the user can easily charge the payment to her mobile carrier bill or credit card. When completed, the app delivers the product.

The payment starts and finishes in the client but further processing and notifications happen server side.

At the moment, the API is experimental and it might change drastically, McMillan said. But Mozilla's aim is to start processing live payments on the first Firefox OS phones and evolve the API quickly from real world usage, he added.

For now, developers are able to simulate payments and test out the code in the Firefox Marketplace, he said.

At the moment details about how merchants should interact with payment providers in the API are not yet specified, said McMillan. The first Firefox OS phones will have a whitelist of allowed payment providers, but that is also not ideal, he added.

"Mozilla plans to work with other vendors through the W3C to reach consensus on a common API that supports web payments in the best way possible," McMillan wrote. When the payments API is shipped with Firefox OS, Mozilla plans to add the API to Firefox for Android and desktop Firefox, he added.