What is the PBO file format?
.pbo files are associated with various computer games published by Bohemia Interactive, including the *Arma* series and *DayZ*. The name stands for Packed Bank of Files.
.pbo files are file containers that can store various game files, including:
- new missions and custom campaigns,
- game character models and locations,
- game scenarios and world data,
- scripts, configs, and engine assets.
PBO format follows a standardized structure consisting of a header entry table, a data section, and a 20-byte SHA-1 checksum appended at the end. PBO packages can hold game-specific files such as SQF scripts, .sqm mission definitions, .p3d models, .paa textures, and config.cpp configs. Entries are usually stored uncompressed, though per-entry LZSS-style compression is supported.
.pbo files are typically created using dedicated editors which allow users to create game mods based on available game assets and resources. Users can design custom missions and campaigns, then export the content as .pbo packages using tools like Arma 3 Tools (Addon Builder) or PboProject.
.pbo files can be unpacked using dedicated tools such as PBO Manager or Mikero's Tools (DePbo). Popular programming languages also offer libraries for working with .pbo files. Multiplayer servers verify addon authenticity using paired .bisign and .bikey signatures.
Security & safety
RISK: MEDIUMA PBO is game data, but mods can contain scripts (.sqf) that run inside the game engine, and the Bohemia engine is powerful enough that malicious mission/addon scripts have been used to grief or attack multiplayer servers. Only install PBOs from reputable sources (Steam Workshop, well-known mod communities); be wary of random .pbo downloads. The signature system (.bisign/.bikey) exists so servers can enforce verified, unmodified addons. Unpacking a PBO to inspect it (PBO Manager) is itself low-risk - it's reading an archive.
Format details
in a nutshellPrograms that open PBO files
Windows5 apps
ArmA / Arma 3 / DayZ (the game itself)
Paid Place the .pbo in the game's Addons or a mod's @Mod/Addons folder (or subscribe via Steam Workshop) - the game loads it directly; no manual unpacking needed to play.
PBO Manager
Free Right-click the .pbo > Extract to unpack it into a folder, or use it to repack a folder into a .pbo. The standard community unpacker (note: Armaholic is archived; mirror via the BI Forums/Steam).
Mikero's Tools (DePbo / PboProject)
Freemium Command-line/GUI tools to unpack (DePbo) and binarize/pack (PboProject) PBOs - the modder-grade toolset.
Arma 3 Tools (Addon Builder)
Free Bohemia's official free toolset on Steam: Addon Builder packs folders into signed PBOs; the supported way to create them.
Eliteness / cpbo (legacy unpackers)
Free Older community PBO tools for browsing/extracting - still work for simple PBOs; prefer Mikero's current tools. 
Linux1 app
Bohemia dedicated server / armake (open-source)
Open-source armake unpacks/packs PBOs on Linux from the command line - useful for server-side modding and CI. Technical details
deep spec| Container type | Flat archive (bank) - entries stored sequentially; folder hierarchy encoded in filename strings |
| Byte order | Little-endian |
| Encoding | Binary |
| Default compression | STORED (uncompressed); optional per-entry LZSS-style compression |
| Integrity check | 20-byte SHA-1 hash of concatenated file data appended at archive end |
| Addon signing | External .bisign / .bikey public-key signature pair used by multiplayer servers to validate PBO authenticity |
| Binary structure | Entry table (filename, packing method, original size, packed size, reserved, Unix timestamp per file) → concatenated data → 20-byte SHA-1 |
| Version marker | Optional 'Vers' properties header entry (null name, packing method 0x56657273) carries prefix and product metadata |
| Encrypted variant | .ebo - encrypted PBO used by Bohemia for protected official game content |
| Supported engines | Real Virtuality (Operation Flashpoint, Arma, Arma 2, Arma 3); DayZ (Enfusion engine) |
| Typical file size | A few kilobytes (simple mission) to several gigabytes (large addon bank) |
| Entry count limit | No hard specification limit; large addon PBOs routinely contain thousands of files |
| Supported platforms | Windows (primary); Linux via dedicated server and armake |
| Common internal files | .sqf scripts, .sqm mission files, .p3d models, .paa textures, config.cpp configs, .rvmat materials |
| Magic bytes / identification | No universal magic number; version variant starts with null-name entry followed by 'Vers' (0x56 0x65 0x72 0x73) at byte offset 4 |
| Runtime behavior | Engine reads .pbo directly at startup without extracting; files accessed by virtual path inside the archive |
| Released | 2001 (Operation Flashpoint: Cold War Crisis) |
| Latest version | PBO format as used by the Real Virtuality / Enfusion engines through Arma 3 and DayZ |
| Specification | community.bistudio.com |
PBO conversions
Community Q&A
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