What is Stock ROM and Custom ROM for Android?

ROM to Android is abbreviated for Read Only Memory. A "ROM" is the operating system software that runs your Droid. It is stored in the “Read Only Memory” portion of the hardware on the Android smartphone and/or tablet. Android comes in two forms: Stock ROM and Custom ROM.

Stock ROMs are the ones which come by default in Android phones or tablets. These are customized versions of Android developed by manufacturers and carriers to let users stick to their devices with unique looks and features. The "out-of-the-box" smartphones are all shipped with stock ROM.

Main Advantages of Stock ROM

1. Keep the warranty. Stock ROMs would not void your warranty of Android devices. One of the biggest reasons why users don't go for the custom ROMs is that rooting will immediately void your warranty. Installing a custom ROM needs to get a root access. Most of Manufacturers prohibit rooting or installing a custom Android version.
2. Pre-installed apps. Android devices with stock ROMs usually come with lots of pre-installed apps. These apps sometime are good enough to attract customers such as music players, live wallpapers, app store, calendar, weather and so on. However, these pre-installed apps sometime are seldom used by users which are called bloatwares. In that, this advantage may turn into disadvantage.
3. Premium Features. Just like the pre-installed apps, Stock ROMs also come with lots of premium features which are not available in custom ROMs. These features include home screen, font, launcher or app drawer. Devices which developed by different manufacturers shiped different premium features and apps.

Custom ROMs are the ones which are customized or developed from the original source code of Android. Custom ROMs are not provided by Google or other mobile vendors but are developed and maintained by community and its contributors. The developed Custom ROMs differ from the original source code in features and looks.

Main Advantages of Custom ROM

1. Root access. Custom ROMs provide you root access of your Android system. If you own an Android with stock ROM and want to get rid of the stock ROM to enjoy the custom one, first you need to root your Android. A custom ROM enables you to do anything in your phones or tablets.
2. Quick updates. Once the latest Android version releases, the stock ROM enables you to update to the newest one without waiting. Stock ROMs controlled by the manufacturers or carriers may don't provide this update service or take long time to do it.
3. Better performance. Custom ROMs let you install third-party apps you like without any limitations and remove any system apps which can't be uninstalled in stock ROM. That's make custom ROM perform and function better than stock ROM. With custom ROMs, users themselves can customize the home screen, font, UI, UX, anything they prefer. An user will become the master of the Android device with the custom ROM. How to install a custom ROM, please refer to: Install a Custom ROM.

Root is the superuser. Your Android phone uses Linux permissions and file-system ownership. You are a user when you sign in, and you are allowed to do certain things based on your user permissions. Root is also a user. The difference is the root user (superuser) has permissions to do anything to any file any place in the system. Rooting is jail-breaking for Androids, and allows users to dive deeper into a phone’s sub-system. If you are available to replace the stock ROM to a custom ROM untill you get a root access. How to Root Android, please refer to: How to Root Android with KingoRoot.