Android is full of complicated-sounding names for parts of their phones. It’s easy to get lost in a haze of technical jargon and carryovers from Linux which make sense to sys-admins and no one else. Open-source enthusiasts tend to be a club exclusively of programmers who already understand these things. For the casual user looking into rooting his/her phone for the first time, the terms can be intimidating.

We’re going to help clear the air and explain once and for all exactly how a bootloader works. What is a bootloader? What does it load? Why do people freak out about it being locked? Don’t worry if you don’t know the answer to these questions. We’ll dig into all that and more below. There’s even a bonus rant against the carriers with regards to bootloaders. Not that we’re thinking of anyone in particular Verizon.

What’s a bootloader?

In the simplest terms, a bootloader is a piece of software that runs every time your phone starts up. It tells the phone what programs to load in order to make your phone run.


The bootloader starts up the Android operating system when you turn on the phone. This is a pretty important job, so it’s very important that nothing goes wrong with it. That’s why phones keep their bootloaders stored in special stable memory.

Alternatively, the bootloader can start up recovery mode. When a phone is in recovery, it can execute large pieces of code that totally rewrite the Android operating system.

The bootloader is important because it loads both of these pieces of software. Without a working bootloader, your phone is a useless brick.

Why unlocked bootloaders are important

Some bootloaders, however, contain an extra layer of security that checks to make sure that it only loads an operating system that passes its approval process.


The exact process of checking for unauthorized software varies from phone to phone, but the effects are the same no matter what. You can’t run any operating system the manufacturer did not approve.

A locked bootloader means you can’t install your own OS. For most people, that’s fine. However, if you want to put the latest version of CyanogenMod or any other custom ROM on your phone, a locked bootloader means you can’t.

Locking the bootloader is a very serious practice with some serious implications. It can present a challenge to Android developers and enthusiasts who wish to install custom ROMs or change the phone.

Who locks?

Installing a locked bootloader is becoming less common, although it remains far too prevalent. It can vary from phone to phone and even from carrier to carrier on the same device.

Google seems to understand and respect the users’ wishes. The recently announced Samsung Galaxy S IV with an unlocked bootloader and stock Android is a step in the right direction.


Verizon is especially bad about releasing phones with locked bootloaders. For whatever reason, it feels the need to lock down its phones and prevent users from taking advantage of everything it can do for them.

For example, the Samsung Galaxy S3 shipped with an unlocked bootloader on every carrier except Verizon. The community over at XDA had to work together for months to crack it. Illegal? Yes. Unethical? Well… We’ll leave that judgment up to you.

Big Red gave this official statement:

Verizon Wireless has established a standard of excellence in customer experience with our branded devices and customer service. There is an expectation that if a customer has a question, they can call Verizon Wireless for answers that help them maximize their enjoyment and use of their wireless phone. Depending on the device, an open bootloader could prevent Verizon Wireless from providing the same level of customer experience and support because it would allow users to change the phone or otherwise modify the software and, potentially, negatively impact how the phone connects with the network. The addition of unapproved software could also negatively impact the wireless experience for other customers. It is always a delicate balance for any company to manage the technology choices we make for our branded devices and the requests of a few who may want a different device experience. We always review our technology choices to ensure that we provide the best solution for as many customers as possible.

Make of that what you will.

Final thoughts

Bootloaders are important. They’re an integral part of keeping your phone working. They’re also a critical piece of the puzzle that is custom ROMs. Hopefully carriers and manufacturers will respect users’ wishes in the future and leave the bootloader alone.