What is the KDZ file format?
The .kdz file is a proprietary firmware container developed by LG Electronics for packaging and distributing Android operating system images to LG smartphones and tablets. Each .kdz file wraps one or more .dz archives, which in turn hold compressed partition images - such as boot, system, super, and modem - encoded with zlib/DEFLATE compression.
The format uses a binary, little-endian structure. A .kdz file begins with a 4-byte header length field (0x28050000) followed by a 32-bit magic signature (0x34127856 in little-endian), making it reliably identifiable by its magic bytes. Three format versions exist: V1 (early devices), V2, and V3 (current packaging); the inner .dz stream is also versioned independently.
Typical .kdz files range from 1 GB to 8 GB, representing a complete ROM image for a specific device model and region. Integrity is enforced through per-chunk MD5 and CRC checksums embedded in the .dz records. The official flashing tool, LGUP, validates device model and region codes before applying any firmware update.
Starting with the LG G6 and V30 (2017 and later), LG transitioned newer devices to the .tot firmware format paired with LGUP. LG exited the smartphone business on July 31, 2021, so no new .kdz files are produced; existing packages continue to circulate for device repair, downgrading, and unbricking.
Community tools such as kdztools (Python) enable extraction on Linux without official LG software.
Security & safety
RISK: HIGHFlashing the wrong KDZ (wrong model, wrong region, or a downgrade past anti-rollback) can hard-brick an LG device. Only flash firmware that exactly matches your model and use LG's tools in Download mode with a good cable. Download KDZ files only from reputable firmware mirrors - many "LG firmware" sites bundle adware or serve tampered files. Extraction with kdztools/KDZTool is harmless (read-only); the risk is in flashing.
Format details
in a nutshell- Kaspersky / generic .kdz data file - Some old databases (including this one) mislabel KDZ as a Kaspersky antivirus file; that association is incorrect.
Programs that open KDZ files
Windows4 apps
LGUP
Free Install LGUP + your model's DLL, put the phone in Download mode, select the .kdz and flash (Refurbish/Upgrade).
LG Flash Tool (LGUP legacy)
Free Older models: load the .kdz, set CSE/region, connect in Download mode and flash.
KDZTool
Open-source Command line: extract the .dz and partition images from V1/V2/V3 KDZ, or repack a modified one.
LG Firmware Extract Tool
Free Windows GUI: select the .kdz/.dz to extract its contents without flashing. 
Linux1 app
kdztools (Python)
Open-source python unkdz.py -f file.kdz -x then python undz.py -f file.dz -s to dump partitions. Technical details
deep spec| Container type | Proprietary binary firmware container wrapping one or more DZ archives |
| Byte order | Little-endian |
| Magic bytes | 0x28050000 (4-byte header length) followed by 0x34127856 (32-bit magic signature) at offset 0 |
| Format versions | V1 (early devices), V2, and V3 (current); inner DZ stream is independently versioned |
| Compression | zlib/DEFLATE applied per partition chunk inside the embedded .dz stream |
| Encryption | None on legacy KDZ; some newer LG packages include signed or obfuscated records |
| Typical file size | 1 GB to 8 GB (full ROM image for one specific device model and region) |
| Internal structure | KDZ header + record table + embedded DZ archive containing compressed partition images (boot, system, super, modem, and others) |
| Integrity verification | Per-chunk MD5 and CRC checksums in DZ records; LGUP validates device model and region before flashing |
| Partition coverage | boot, system, super, modem, and other Android partitions for a complete device ROM |
| Developer | LG Electronics |
| Tool platforms | Windows (LGUP, KDZTool, LG Flash Tool); Linux (Python kdztools) |
| MIME type | application/octet-stream |
| Superseded by | TOT firmware format with LGUP for LG G6, V30, G7, and later models (2017+) |
| Production status | Discontinued; LG exited the smartphone business on July 31, 2021 - no new KDZ files are issued |
| Released | c. 2011 (LG Android smartphone era) |
| Latest version | KDZ format V3 (current LG packaging) |
| Specification | github.com |
KDZ conversions
Community Q&A
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