AT&T has released Android 5.1.1 update for its Nexus 6 users. Reuters/Gustau Nacarino

Google finally introduced its long-rumored Android M operating system Thursday at its I/O 2015 event in San Francisco -- and it includes six key changes over previous versions. Most of the improvements reportedly revolve around the way apps interact with one another. To top it off, Android M's mobile-based payment system has been enhanced via the inclusion of fingerprint sensor support. While the Android M preview version for developers is available now, the final version for the general public will be released later this year. Here are the six killer features of Android M collated by GSM Arena.

Changes To App Permissions

Google’s Android M has taken a cue from Apple’s iOS permissions. This means an Android M device user will not be asked about all the app permissions together during the installation time. Alternatively, the app will request for permission when logging in for the first time. Meanwhile, users can navigate to the Settings screen to check out the list of permissions an app uses and in turn, the permissions can be revoked or allowed, according to GSM Arena.

Custom Chrome Tabs For Web Views

In general, apps use Web components that make the user switch between a browser and the app, in case the user is asked to open a link embedded within the app. In some cases, the Web view is embedded into the app. In order to make it less clumsy, the Android M users can now style Chrome to make it look like it is part of the Web. This means the app can launch a custom Chrome tab and customize/style the required buttons to make it look like a native part of the app.

Secured Opening Of App Links

In case apps want to interact with any other service or system other than a browser, Android M has a secured way to make it work. The new OS comes with a mechanism for apps to check whether the received request (e.g. opening a link) is legitimate or not. Android M will reportedly “verify it cryptographically with the Web server” before allowing the link.

Mobile Payment System: Android Pay

Similar to Apple Pay and Samsung Pay, Google has Android Pay to shake up the mobile payment system. Android Pay uses the handset’s NFC connectivity to enable the payments. This payment system will reportedly work with all major cards and carriers like AT&T, T-Mobile and Verizon in the U.S. Additionally, it will also work in McDonald's, Best Buy, Subway, Coca Cola and Pepsi, among others.

Native Fingerprint Sensors

Google has officially made fingerprint sensor functionality part of the Android M OS. Needless to say, this consistent API will make the work of developers and OEMs easier.

Improved Battery Life, Quick Charging Features

Android M comes with improved battery life via Doze. Reportedly, the Android phones will utilize the motion sensors to figure out when the handset is not in use. Therefore, with Doze, the active apps will check with the servers and in turn, the background activities will be made less active, during the idle time. In any case, the phone can reportedly be awakened quickly.

Furthermore, Google has opted for the USB Type C standard for the new power delivery modes. This means the Android M handsets can be charged faster than the phones running on Android L.