Bootloader unlocking is the process of disabling the

bootloader A bootloader, also spelled as boot loader or called boot manager and bootstrap loader, is a computer program that is responsible for booting a computer. When a computer is turned off, its softwareincluding operating systems, application code, an ...

security that makes

secure boot UEFI (Unified Extensible Firmware Interface) is a set of Specification (technical standard), specifications written by the UEFI Forum. They define the Software architecture, architecture of the platform firmware used for booting and its Interfa ...

possible. It can make advanced customizations possible, such as installing a

custom firmware Custom firmware, also known as aftermarket firmware, is an unofficial new or modified version of firmware created by third parties on devices such as video game consoles and various embedded device types to provide new features or to unlock hidden f ...

. On smartphones this can be a custom Android distribution or another

mobile operating system A mobile operating system is an operating system for mobile phones, tablets, smartwatches, smartglasses, or other non-laptop personal mobile computing devices. While computers such as typical laptops are "mobile", the operating systems used on ...

. Some bootloaders are not locked at all, others can be unlocked using a standard command, others need assistance from the manufacturer. Some do not include an unlocking method and can only be unlocked through a software

exploit Exploit means to take advantage of something (a person, situation, etc.) for one's own end, especially unethically or unjustifiably. Exploit can mean: *Exploitation of natural resources *Exploit (computer security) * Video game exploit *Exploitat ...

. Bootloader unlocking is also done for mobile forensics purposes, to extract

digital evidence In evidence law, digital evidence or electronic evidence is any probative information stored or transmitted in digital form that a party to a court case may use at trial. Before accepting digital evidence a court will determine if the evidence ...

from mobile devices, using tools such as

Cellebrite UFED The UFED (Universal Forensics Extraction Device) is a product series of the Israeli company Cellebrite, which is used for the extraction and analysis of data from mobile devices by law enforcement agencies. Products Cellebrite sells various pr ...

Background

Unlocking the bootloader usually voids any warranties and may make the device susceptible to data theft. On Chromebooks, enabling developer mode makes the system less secure than a standard laptop running Linux. Unlocking the bootloader may lead to data loss on Android and ChromeOS devices, as some data is impossible to back up without root permission. Sascha Segan from

PCMag ''PC Magazine'' (shortened as ''PCMag'') is an American computer magazine published by Ziff Davis. A print edition was published from 1982 to January 2009. Publication of online editions started in late 1994 and have continued to the present d ...

considered a locked bootloader a mistake on the Qualcomm Snapdragon Insiders phone, which is targeted at advanced users.

Platforms

Android

Unlocking the bootloader is typically done during the process to obtain ''root'' access.

History

The bootloaders of Nexus and Pixel devices can be unlocked by using the

fastboot Fastboot is a protocol and a tool of the same name. It is included with the Android SDK package used primarily to modify the flash filesystem via a USB connection from a host computer. It requires that the device be started in Fastboot mode. If ...

command oem unlock. When Motorola released a bootloader unlocking tool for the Droid Razr, Verizon removed the tool from their models. In 2011,

Sony Ericsson Sony Mobile Communications Inc. ( ja, ソニーモバイルコミュニケーションズ株式会社) was a multinational telecommunications company founded on October 1, 2001, as a joint venture between Sony Group Corporation and Ericsson. I ...

released an online bootloader unlocking tool. Sony requires the IMEI number to be filled in on their website. For the Asus Transformer Prime TF201, Asus has released a special bootloader unlock tool. In 2012, Motorola released a limited tool for unlocking bootloaders. They require accepting terms and conditions and creating an account before the bootloader can be unlocked for a Moto G. HTC phones have an additional layer of lock called "S-OFF/S-ON". Bootloaders can be unlocked using an exploit or using a way that the vendor supplied. The latter method usually requires wiping all data on the device. In addition, some manufacturers prohibit unlocking on carrier locked phones. Samsung's US and Canadian Snapdragon phones do not allow unlocks regardless if the phone was bought from a carrier or not. In 2018, a developer from

XDA Developers XDA Developers (also known simply as XDA; often stylized as xda-developers) is a mobile software development community launched on 20 December 2002. Although discussion primarily revolves around Android, members also talk about many other opera ...

launched a service which allowed users to unlock the bootloader of some Nokia smartphone models.Similarly, another developer from

launched a service to allow users to unlock the bootloaders of

Samsung Galaxy S20 The Samsung Galaxy S20 is a series of Android-based smartphones designed, developed, marketed, and manufactured by Samsung Electronics as part of its Galaxy S series. They collectively serve as the successor to the Galaxy S10 series. The first ...

and

Samsung Galaxy S21 The Samsung Galaxy S21 is a series of Android-based smartphones designed, developed, marketed, and manufactured by Samsung Electronics as part of its Galaxy S series. They collectively serve as the successor to the Samsung Galaxy S20 series. T ...

Phones.

Huawei Huawei Technologies Co., Ltd. ( ; ) is a Chinese multinational technology corporation headquartered in Shenzhen, Guangdong, China. It designs, develops, produces and sells telecommunications equipment, consumer electronics and various smar ...

announced plans to allow users to unlock the bootloader of the Mate 30 series, but later retracted that. Huawei has stopped providing bootloader unlock codes since 2018. A bootloader exploit named checkm30 has been developed for

HiSilicon HiSilicon () is a Chinese fabless semiconductor company based in Shenzhen, Guangdong and wholly owned by Huawei. HiSilicon purchases licenses for CPU designs from ARM Holdings, including the ARM Cortex-A9 MPCore, ARM Cortex-M3, ARM Cortex-A7 M ...

based Huawei phones. When the bootloader of the

Samsung Galaxy Z Fold 3 The Samsung Galaxy Z Fold 3 (stylized as Samsung Galaxy Z Fold3, sold as Samsung Galaxy Fold 3 in certain territories) is a foldable smartphone that is part of the Samsung Galaxy Z series. It was revealed by Samsung Electronics on August 11, 2 ...

was unlocked, the camera became less functional. This could be restored by re-locking the bootloader. This issue was later fixed by Samsung. For the

Samsung Galaxy S22 The Samsung Galaxy S22 is a series of Android-based smartphones designed, developed, manufactured, and marketed by Samsung Electronics as part of its Galaxy S series. Unveiled at Samsung's Galaxy Unpacked event on 9 February 2022. They collec ...

series, unlocking the bootloader has no effect on the camera.

Others

Microsoft

The WPInternals tool is able to unlock bootloaders of all

Nokia Lumia Microsoft Lumia (previously the Nokia Lumia) is a discontinued line of mobile devices that was originally designed and marketed by Nokia and later by Microsoft Mobile. Introduced in November 2011, the line was the result of a long-term partnersh ...

phones running

Windows Phone Windows Phone (WP) is a discontinued family of mobile operating systems developed by Microsoft for smartphones as the replacement successor to Windows Mobile and Zune. Windows Phone featured a new user interface derived from the Metro design la ...

, but not phones like the

Alcatel Idol 4 Alcatel Idol 4 and Idol 4S are smartphones manufactured by TCL Corporation and marketed by Alcatel Mobile Phones. They were unveiled during Mobile World Congress in February 2016, and are a successor to the Idol 3. The Idol 4 and 4S are positioned ...

HP Elite x3 HP Elite x3 is a premium Windows 10 Mobile smartphone produced by Hewlett-Packard. It was officially announced on February 21, 2016, and released later that year. Specifications The HP Elite x3 was built for enterprise users with several enterp ...

. Version 1.0 was released in November 2015. In October 2018, the tool was released as open source software when the main developer René Lergner (also known as HeathCliff74) stepped down. The slab bootloader used by Windows RT could be unlocked using a vulnerability, but was silently patched by Microsoft in 2016. UEFI Secure Boot on x86 systems can generally be unlocked.

Apple

The boot ROM protection on iOS devices with an A11 processor or older can be bypassed with a hardware exploit known as checkm8, which makes it possible to run other operating systems including Linux. The bootloader on M1 based Macs can be unlocked.

Google

The equivalent of bootloader unlocking is called developer mode in

Chromebooks A Chromebook (sometimes stylized in lowercase as chromebook) is a laptop or tablet running the Linux-based ChromeOS as its operating system. Initially designed to heavily rely on web applications for tasks using the Google Chrome browser, Chromeb ...

. Chromebooks use custom bootloaders that can be modified or overwritten by removing a Write-protect screw. In 2013, the bootloader of the

Chromecast Chromecast is a line of digital media players developed by Google. The devices, designed as small dongles, can play Internet-streamed audio-visual content on a high-definition television or home audio system. The user can control playback with ...

was hacked using an exploit. In 2021, it was hacked again for newer versions.

SpaceX

In August 2022, security researcher Lennert Wouters applied a voltage injection attack to bypass firmware verification of a

Starlink Starlink is a satellite internet constellation operated by SpaceX, providing satellite Internet access coverage to 45 countries. It also aims for global mobile phone service after 2023. SpaceX started launching Starlink satellites in 2019. As ...

satellite dish from

SpaceX Space Exploration Technologies Corp. (SpaceX) is an American spacecraft manufacturer, launcher, and a satellite communications corporation headquartered in Hawthorne, California. It was founded in 2002 by Elon Musk with the stated goal of ...

Relocking

On Android, it is possible to relock the bootloader.

Explanatory notes

References

External links

Locking/Unlocking the Bootloader

Android Open Source Project Android is a mobile operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen mobile devices such as smartphones and tablets. Android is developed by a consortium of ...

Qualcomm’s Chain of Trust
{{Firmware and booting Android (operating system) Hardware restrictions Windows Phone IOS Microsoft Windows security technology