How to unpack Android firmware: a complete overview of tools

Modification of Androiddevices often requires deep intervention in the software structure, and the first step on this path invariably becomes access to the contents of factory images. Users who want to install a custom recovery, add root access, or simply study the internal structure of their system are faced with the need to extract data from firmware archives. However, standard archivers that are familiar to us in everyday life are often powerless here or do not work correctly.

The specificity of firmware files lies in the use of specific compression and encryption formats, which differ from conventional ZIP or RAR. Developers use a variety of containers to optimize space and protect data integrity, so choosing the right tool depends on which extension you're dealing with. The wrong approach can lead not only to an error when opening, but also to damage to the files, which will make further work with the image impossible.

In this article we will look in detail at how to unpack Android firmware depending on its format, consider professional utilities and scripts, and also discuss the nuances of working with partitions system, boot i vendor. Understanding the file structure is half the success in modding, so it is important to understand extraction methods before you begin active operations with the device.

Analysis of firmware file formats

Before running any app, you must clearly identify the type of file you downloaded. Firmware for different manufacturers of smartphones and tablets are distributed in completely different containers, and there is no universal “key” for everyone. Often, users try to open the image as a regular archive, which results in an “unknown format” error, although there may be a completely readable structure hidden inside.

The most common extensions you will encounter include .zip, .tar or .tar.md5 (typical for Samsung), as well as raw images .img. More complex cases include files .dat, .br or .new.dat.brthat are used in modern OTA updates and require specific decompression algorithms. Misidentification of the file type is the main cause of failures at the initial stage.

To accurately determine the file type, it is recommended to use a HEX editor or specialized analysis utilities, but often it is enough to look at the extension and know the device manufacturer. For example, files for Xiaomi often have a structure .tgz inside .zip, and for Huawei there are specific .app or .bin packages. Understanding the origin of the file will tell you which tool to choose.

• 📦 ZIP/TGZ —standard archives, often containing other formats or update scripts inside.
• 💾 TAR/TAR.MD5 —containers used by Samsung, which contain individual partition images.
• 🗄️ IMG/DAT/BR —raw images of file systems or compressed blocks of data that require conversion.

⚠️ Attention: Never rename file extensions manually in the hope that the app will “see” them. This will not change the internal data structure and is guaranteed to lead to an error when trying to unpack.

Working with ZIP and TAR archives

The simplest scenario is working with firmware packaged in standard archives .zip or .tar. Classic archive managers, such 7-Zip, WinRAR or built-in tools of the Windows operating system, are suitable for these purposes. In most cases, just right-click and select "Extract All" to access the internal files.

However, if there are files inside the archive with extensions .new.dat or .patch.dat, simple extraction will not give you access to the file system. These files are part of the A/B (Seamless Updates) update mechanism and require additional processing by specialized scripts. A standard archiver will only take them out of the container, but will not decrypt the contents of the section. When working with Samsung archives, you should be careful about checksums. Files with the extension system.

When working with .tar With archives from Samsung, you should be attentive to checksums MD5. Files with the extension .tar.md5 are a regular TAR archive, to which a hash sum is appended to the beginning or end to check integrity. Some apps may complain about this format, so before opening it in an archiver, you may need to remove extra hash bytes using a HEX editor.

To further study the structure of the system, you will need to go to work with images sections, which will be discussed in the following sections.

apps for unpacking IMG and DAT images

When standard archivers are powerless, specialized utilities designed for working with file system images come onto the scene. Files with the extension .img often represent an exact copy of a memory section (for example, system.img or userdata.img). There are powerful tools for opening them and extracting files, such as Android Image Kitchen or Ext4Unpacker.

app Android Image Kitchen is one of the most popular solutions due to its graphical interface and support for many formats. It allows you not only to unpack system.img into a regular folder with files, but also to pack the changed data back into a ready-made image for flashing. This is an indispensable tool for those who plan to remove system software (bloatware) or add their own applications.

For file formats .dat and .br (Brotli compression), which are often found in official updates of Google Pixel and other stock Android, converters are required. Utilities like sdat2img and br_to_img convert these specific blocks into a understandable format .imgwhich can then be opened in Image Kitchen. The process often requires the use of the command line, which may seem difficult for beginners.

Utility	Supported formats	Difficulty of use	Features
Android Image Kitchen	IMG, DAT, BR	Low (GUI)	Allows packing and unpacking
7-Zip	ZIP, TAR	Very low	Only for containers, not for images
sdat2img.py	NEW.DAT	Medium (Python)	Requires a transfer_list file
Yaffs2 Viewer	YAFFS2	High	For older Android devices 2.x-4.x

Where can I find transfer_list?

The transfer_list file is usually located in the same firmware archive as the .new.dat file. It is necessary for the sdat2img script to correctly restore the file system structure, since it contains information about which blocks to write where.

Using the command line and scripts

Advanced users often prefer to use console utilities, as they provide greater control over the process and are less dependent on graphical shells. Working through the Windows command line or Linux terminal allows you to automate the unpacking process using batch files .bat or scripts .sh. This is especially true when processing large amounts of data or batch conversion.

To work with images, tools from Android SDK Platform Toolsare often used, in particular utilities simghdr for checking headers and simg2img for converting sparse images into raw ones. Sparse images are used to save space and speed up the firmware process, but are not available for direct viewing without conversion.

A typical scenario for working in the console is as follows: first we convert the sparse image to raw, then mount it or use the extraction utility. The commands may look cumbersome, but they guarantee results where graphical apps may fail due to incompatible library versions.

simg2img system.img system_raw.img
python sdat2img.py transfer_list system.new.dat system.img

When using Python scripts such as unpack bootimg, it is important to ensure that all necessary dependencies are installed on the computer and the environment variables are configured correctly. The “Python not found” error or missing modules is a common problem that beginners encounter when they first try to run the bootloader unpacking script boot.img.

⚠️ Attention: When working with scripts on the command line, carefully monitor the paths to the files. Using Cyrillic in folder names or spaces in paths often causes the command to fail.

Unpacking the Boot and Recovery loader

Unpacking the bootloader image boot.img and the recovery partition recovery.img. These files have a unique structure, different from the file system ext4, and consist of a header, a core (kernel) and a ramdisk (ramdisk). To analyze them, specialized utilities are used, such as AJB (Android Image Packer) or MagiskBoot.

The unpacking process boot.img is necessary if you want to modify the kernel, add drivers, or inject root access directly into the image. The utility MagiskBoot, which is part of the popular superuser rights manager, can not only decompose the image into its components, but also patch it to obtain access rights, which makes it a universal tool in the modder's arsenal.

Ramdisk (ramdisk.cpio.gz) is a compressed archive containing the files necessary for the initial download systems. After extracting it from the boot image, it can be opened with any archiver that supports the format cpio or gzip. Changing files inside the ramdisk allows you to manage access rights to files and initialization processes at the very early stage of turning on the smartphone.

• 🔑 Kernel — the system kernel that controls the hardware of the smartphone.
• 📂 Ramdisk — a temporary file system in RAM.
• 🛡️ DTB — a device tree that describes the hardware configuration.

It is worth noting that on devices with a locked bootloader or verification enabled AVB (Android Verified Boot), modifying the boot image will cause the device to refuse to boot. In such cases, you must first unlock the bootloader or disable signature verification, which is not possible on all smartphone models.

Frequent errors and problems during unpacking

Even with the right software, users often encounter errors during the unpacking process. One of the most common problems is a mismatch between utility versions and image formats. For example, trying to open an image from Android 14 with a utility written during Android 6 is almost guaranteed to lead to a crash of the app or the receipt of “broken” files.

Another common mistake is ignoring partition tables. The firmware file may contain several images merged into one, or have offsets that must be taken into account manually. If the app produces an “Invalid header” or “Unknown format” error, it is worth checking whether the file is part of a larger container or whether it is encrypted by the manufacturer.

Problems can also arise due to insufficient access rights. When working in Windows, sometimes you need to run apps as an administrator, especially if they try to create files in the root directories of disks. In a Linux environment, similarly, you may need to use sudo to mount images or write files.

⚠️ Attention: If the utility hangs at 99% of the unpacking process, do not rush to force close it. Large system images can take several minutes to process, and freezing may be a sign of active disk activity rather than a failure.

If unsuccessful, it is recommended to try an alternative tool. What the graphical shell could not do is often successfully accomplished by the console utility, and vice versa. Developer communities on forums like 4PDA or XDA Developers often release patches for popular apps that correct errors with specific device models.

What to do if the file is damaged?

If you receive a CRC or corrupted data error when unpacking, try downloading the firmware from another source. A common reason is incomplete downloading of the file due to unstable Internet. Check the MD5 hash of the downloaded file with the official one.

FAQ: Questions and answers

Is it possible to unpack the firmware directly on a smartphone without a computer?

Theoretically, this is possible using terminal emulators and special scripts, if the device has root access. However, in practice this is extremely inconvenient due to the low speed of the smartphone processor during archiving and the lack of a full-fledged file manager for working with images. It is recommended to use a PC.

Is it safe to edit files inside the unpacked firmware?

Editing is safe for your computer, but making changes to system files (especially in build.prop or system libraries) can lead to the smartphone being “bricked” during subsequent firmware update. Always make a backup copy of the original files before changing.

Why do I see only hieroglyphs instead of text after unpacking?

You are trying to open a binary file (disk image) in a text editor. Files .img or .dat are not text documents. They must first be correctly unpacked with a specialized utility into a regular folder with files, and only then open specific configs or scripts.

Do you need to delete .md5 files before flashing the firmware via Odin?

No, the Odin app is specifically designed to work with files .tar.md5. It automatically reads and checks the hash before starting to write. Removing the .md5 part may only be necessary for third-party archivers, but not for the firmware tool.

Where can I find drivers for the decompression mode?

Drivers are not needed to decompress files on the computer, since this is working with files on the disk, and not with a connected device. Drivers (ADB/Fastboot) will only be needed at the stage when you decide to write the modified image back to the smartphone’s memory.