Nexus devices have locked bootloaders too, but they are easy to unlock.

HTC and Sony devices generally come with locked bootloaders but these companies also provide the option to unlock it on their developer portals.

While some OEMs/carriers remain rigid with locking the bootloader to discourage custom development, there are still many who do not use such tricks. In the same way, when a device manufacturer wishes to ensure that its users must root their devices and replace the official recovery with a custom one, they ship their phones or tablets with locked bootloaders. Most carriers do not like their users to break with the contract by using a SIM card from another carrier. Both the things are put into a device to discourage the users from being infidel to their network carriers and OEMs respectively. When we talk of an “unlocked” phone in the context of an Android device, it might have two implications: a phone with unlocked SIM capabilities, or a phone that has an unlocked bootloader.

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