Backpack Asset Reference

Intermediate40-60 minutesWindowsNotepad++Unity Editor

Backpacks are the primary wearable storage expansion in Unturned™. A backpack asset defines a container that the player wears on the back slot, expanding the player's inventory by a rectangular grid of slots. Unlike placeable containers (crates, lockers, safes), a backpack travels with the player and is always accessible from the inventory screen while equipped. Every survival-oriented mod - from a civilian daypack to a military cargo rucksack - is a backpack asset.

This article is the 57 Studios™ canonical reference for the backpack asset type. It covers every .dat field specific to the backpack subclass, the inheritance chain from ItemBagAsset through ItemClothingAsset to ItemBackpackAsset, the storage grid dimensions and capacity math, the slot assignment system, the distinction between the backpack slot and vest storage, the Pro flag and economy item behavior, the blueprint system for salvage and repair, and common authoring pitfalls. The shared fields that appear on every item asset (ID, GUID, Rarity, Slot, Size_X, Size_Y) are documented in Item Asset Anatomy; this article focuses on the fields that are unique to the backpack subclass and the fields inherited from ItemBagAsset.

Documentation source: This article references the official Smartly Dressed Games modding documentation for class hierarchy and field definitions. The game-file evidence set includes 50+ shipped backpack .dat files from the vanilla Unturned asset set, examined for field vocabulary and value ranges.

Who this article is for

This article is written for Unturned™ mod authors who have already completed at least one item mod of any type and are familiar with the master bundle pipeline and .dat authoring workflow. If you are new to Unturned™ modding, start with Item Asset Anatomy and Project Folder Structure and GUIDs before returning here. Familiarity with the clothing system (especially the Backpack slot) is recommended; the Clothing Asset Reference covers the slot-level details that this article extends.

What you will learn

• The inheritance hierarchy: ItemBagAsset as the base, ItemBackpackAsset as the concrete type.
• Every .dat field that a backpack asset uses, with real shipped values from the vanilla game files.
• How the storage grid (Width and Height fields) determines slot capacity and how to calculate the total.
• The distinction between Width/Height (bag-level storage) and Storage_X/Storage_Y (clothing-level storage extension).
• How the Pro flag, Bypass_ID_Limit, Proof_Water, and other edge-case fields behave on backpack assets.
• The blueprint system for salvage and repair on backpacks, as authored in the shipped game files.
• How the Backpack slot interacts with the Vest slot for combined storage.
• The visual mesh considerations for large backpacks and their effect on player silhouette.
• A complete worked example: authoring a custom military rucksack from scratch.

How the backpack system works

The Unturned™ backpack system sits at the intersection of the clothing system and the storage system. When a player equips a backpack, the Unturned™ runtime loads the item's .dat file, instantiates the backpack prefab on the character skeleton at the Character_Spine1 and Character_Spine2 bones, and extends the player's inventory by a rectangular grid whose dimensions are defined by the Width and Height fields (inherited from ItemBagAsset). The backpack storage grid is accessible from the inventory screen while the item is equipped; unequipping the backpack removes the grid expansion and any items stored in the backpack's slots are returned to the player's main inventory or dropped, depending on available space.

The sequence above shows the equip-time chain. The critical step for mod authors is that the Width and Height fields drive the storage capacity; a backpack with Width 8 and Height 7 (the Alicepack configuration) creates a 56-slot grid. The fields are read once at load time and the grid is created when the item is first equipped.

The storage grid from a backpack is additive with the vest storage grid. A player wearing a backpack with Width 8 and Height 7 (56 slots) and a vest with Storage_X 5 and Storage_Y 4 (20 additional slots) has 76 storage slots from wearable items alone, added to their base inventory capacity. The backpack grid and the vest grid are separate panel regions in the inventory UI.

Class hierarchy

The backpack asset inherits from three parent classes in the following chain:

ItemAsset (base item properties: ID, GUID, Name, Rarity)
  └── ItemClothingAsset (slot assignment, Armor, wearable behavior, Useable Clothing)
      └── ItemBagAsset (Width, Height - abstract base for containers)
          └── ItemBackpackAsset (no unique properties - inherits everything from ItemBagAsset)

The critical implication of this hierarchy is that ItemBackpackAsset introduces no unique fields. Every field a backpack uses comes from one of its parent classes. The ItemBagAsset class provides the Width and Height fields that define the storage grid. The ItemClothingAsset class provides the slot assignment (Type Backpack), the Useable Clothing flag, and any inherited fields from the clothing system. The ItemAsset class provides the identity fields and the shared item system conventions.

ItemBagAsset is the abstract base

The ItemBagAsset class is an abstract base class that is "unusable on its own" according to the official SDG documentation. It exists to provide the Width and Height grid fields that backpacks (and potentially other bag-type items) inherit. You do not author a standalone ItemBagAsset; you author an ItemBackpackAsset. The bag asset article in this series (Bag Asset Reference) documents the base class separately.

Complete .dat field reference

Identity fields (inherited from ItemAsset)

Every backpack requires the standard identity block. These fields identify the item to the engine and to the asset registry.

Field	Type	Example	Required	Purpose
ID	uint16	5001	Yes	Numeric item ID. Must be unique across all loaded mods. Use IDs in the 50000+ range to avoid collision with vanilla and established community mods.
GUID	uint128 hex	a1b2c3d4e5f64a7b8c9d0e1f2a3b4c5d	Yes	128-bit globally unique identifier. Generate a fresh GUID for every new backpack item. Never reuse GUIDs.
Type	enum	Backpack	Yes	Must be Backpack for backpack-type items. This is the value that assigns the item to the Backpack slot.
Name	string	MyMilitaryRucksack	Yes	Internal name. Used in console commands and cross-reference.
Rarity	enum	Uncommon	No	Controls inventory highlight color. Values: Common, Uncommon, Rare, Epic, Legendary, Mythical. Defaults to Common.
Useable	enum	Clothing	Yes	Must be Clothing for all wearable items including backpacks. This flag tells the engine that the item can be equipped to a clothing slot.
Size_X	uint8	2	Yes	Width in inventory grid cells when the item is not equipped.
Size_Y	uint8	2	Yes	Height in inventory grid cells when the item is not equipped.

Storage grid fields (inherited from ItemBagAsset)

These fields define the storage capacity of the backpack. They are inherited from ItemBagAsset, which is the base class that provides rectangular container dimensions.

Field	Type	Range	Example	Purpose
Width	uint8	0-10 (cohort max)	8	Number of columns (horizontal storage slots) in the backpack grid. Values above 10 produce UI clipping on standard player screen resolutions.
Height	uint8	0-10 (cohort max)	7	Number of rows (vertical storage slots) in the backpack grid. Values above 8 produce UI clipping on standard player screen resolutions.

The total storage slot count is Width × Height. An Alicepack with Width 8 and Height 7 provides 56 slots. A Daypack with Width 7 and Height 4 provides 28 slots. A Leather Pack with Width 6 and Height 5 provides 30 slots.

Field name note: Width/Height vs Storage_X/Storage_Y

Backpack assets in the shipped game files use Width and Height for their storage grid dimensions. Some community documentation references Storage_X and Storage_Y as synonyms. The shipped game files (Alicepack, Daypack, Travelpack, Leather_Pack, Pack_Spec_Ops, Dufflebag, Diving_Tank) consistently use Width and Height. The 57 Studios cohort recommendation is to use Width and Height for backpack assets. Vest assets use Storage_X and Storage_Y. The field names are not interchangeable between the two slots.

Size_Z field

Field	Type	Range	Example	Purpose
Size_Z	float	0.0-2.0	0.6	Visual depth scaling factor for the backpack prefab. Controls how far the mesh extends from the player's back. Not a gameplay-affecting field - it is a visual tuning parameter.

The Size_Z field appears on the majority of shipped backpack .dat files. Values observed in the vanilla asset set range from 0.35 (Squid_Backpack, a flat item) to 1.6 (Wings, a large wing-span item). Typical backpacks use 0.55 (Dufflebag variants) or 0.6 (Daypack, Travelpack, Alicepack, most military packs). The field does not affect the storage grid or collision; it only tunes the visual depth scale applied to the prefab when attached to the character skeleton.

Pro flag

Field	Type	Default	Example	Purpose
Pro	flag	not set	Pro	When present, marks the backpack as a PRO/Gold-tier item. Non-PRO players can see and pick up the item but cannot equip it.

The Pro flag is set on many of the vanity and cosmetic backpack items in the shipped asset set: capes, shields, wings, instrument cases, backpacks with no storage grid. Functional backpacks that provide inventory expansion (Alicepack, Daypack, Travelpack, Dufflebag, Leather_Pack, Pack_Spec_Ops) do not carry the Pro flag in the shipped set. The cohort recommendation for Workshop mods is to leave this flag absent on standard functional backpacks and to use it only on cosmetic-only backpack items intended for the PRO economy.

Bypass_ID_Limit flag

Field	Type	Default	Example	Purpose
Bypass_ID_Limit	flag	not set	Bypass_ID_Limit	When present, allows the item to use an ID above the default limit (typically above 2000 in the vanilla engine configuration).

The Bypass_ID_Limit flag appears on two shipped backpack items: HeadlessCape (ID 797) and Squid_Backpack (ID 787). Both are cosmetic backpacks with the Pro flag set. Standard backpacks with IDs in the 200+ range do not require this flag. The cohort recommendation is to add Bypass_ID_Limit to any backpack with an ID above 2000, following the pattern established by the vanilla items that exceed this threshold.

Ignore_NPOT flag

Field	Type	Default	Example	Purpose
Ignore_NPOT	flag	not set	Ignore_NPOT	When present, suppresses the "Non-Power-Of-Two" texture warning for the backpack's textures.

This flag appears on exactly one shipped backpack: Carpat_Lastman_Backpack.dat, accompanied by the comment "Future curated assets should be power of 2, but we ignore warnings for a few pre-warning items." The cohort recommendation is to author textures at power-of-two resolutions and to avoid needing this flag. If you are importing an asset from an external source that uses non-power-of-two textures, include this flag to suppress the engine warning.

Proof_Water flag

Field	Type	Default	Example	Purpose
Proof_Water	flag	not set	Proof_Water	When present, the backpack provides water damage immunity to the wearer.

This flag appears on the Diving_Tank backpack item (ID 1178). The Diving Tank is a specialized backpack that provides underwater breathing capability. The Proof_Water flag is not present on any other backpack in the shipped set. Standard backpack mods should omit this flag unless the design intent is to provide environmental immunity.

Storage grid capacity reference

The following table documents the storage configurations observed in the shipped backpack asset set, ordered by total slot count ascending.

Backpack item	Width	Height	Total slots	Configuration type
Diving Tank	2	4	8	Specialist - minimal storage, environmental purpose
Leather Pack	6	5	30	Medium - crafted leather pack
Daypack	7	4	28	Medium - standard civilian carry
Dufflebag	7	4	28	Medium - standard civilian carry
Travelpack	5	7	35	Medium - tall-narrow format
Pack_Spec_Ops	8	5	40	Large - tactical operations pack
Alicepack	8	7	56	Large - military cargo backpack

Grid aspect ratio considerations

The grid aspect ratio (Width divided by Height) determines how the backpack storage panel appears in the inventory UI. A wide-short grid (Daypack: 7 wide × 4 tall) fills the horizontal space; a tall-narrow grid (Travelpack: 5 wide × 7 tall) fills vertical space. The cohort recommendation is to match the aspect ratio to the backpack's visual shape: a wide, flat dufflebag should use a wide grid; a tall expedition pack should use a tall grid. The visual congruence helps players understand their inventory layout intuitively.

Backpack storage vs. vest storage vs. base inventory

Unturned™ maintains three distinct inventory regions that contribute to the player's total storage capacity:

Region	Source item type	Fields	Slot	Persistence
Base inventory	No item required	Built into the player	N/A	Always present
Backpack storage	Backpack	Width, Height	Backpack slot	Only while backpack is equipped
Vest storage	Vest	Storage_X, Storage_Y	Vest slot	Only while vest is equipped

The three regions are additive. A player wearing a military Alicepack (56 slots) and a tactical vest (20 slots) has 76 inventory slots plus their base capacity. When the player unequips the backpack, the 56 backpack grid slots are removed; any items stored in those slots are moved to the base inventory if space permits, or dropped on the ground if the base inventory is full.

Unequipping a full backpack

When a player unequips a backpack that contains items, those items must move to the base inventory. If the base inventory does not have enough free space, the excess items drop to the ground at the player's feet. This is a data-loss risk for players who unequip a full backpack in a dangerous area. Mod authors should document this behavior in their workshop description or server rules.

Blueprint system for backpacks

Shipped backpack assets frequently include blueprint definitions for salvage and repair. The blueprint system is authored directly in the backpack's .dat file using the Blueprints block syntax. Two blueprint patterns recur across the vanilla backpack set.

Salvage blueprint

The salvage blueprint allows the player to break down a backpack into raw materials. Every backpack in the shipped set that has blueprints includes a salvage entry.

Blueprints
[
  {
    Name Salvage
    CategoryTag "7ed29f9101ae4523a3b2e389414b7bd9" // Salvage
    InputItems this
    OutputItems "14901f32cd3240179fd6124324cc27e5 x 5" // Cloth
    Effect "7eceb9f7751d4634b572c8e236355104" // Rip
  }
]

The salvage blueprint consumes the backpack itself (InputItems this) and produces a quantity of Cloth. The output quantity varies by backpack size:

Backpack	Cloth output	Blueprint pattern
Daypack	4 Cloth	Salvage + Repair
Travelpack	4 Cloth	Salvage + Repair
Dufflebag	3 Cloth	Salvage + Repair
Leather Pack	1 Leather	Salvage only (craftable variant)
Alicepack	5 Cloth	Salvage + Repair
Pack_Spec_Ops	6 Cloth	Salvage + Repair

Repair blueprint

The repair blueprint allows the player to restore a damaged backpack to full condition using raw materials. The repair pattern is consistent across all backpacks that include it:

{
  Name Repair
  CategoryTag "732ee6ffeb18418985cf4f9fde33dd11" // Repair
  Operation RepairTargetItem
  InputItems "14901f32cd3240179fd6124324cc27e5 x 4" // Cloth
  RequiresNearbyCraftingTags
  [
    "2ac5ddc545a848008c0308d21f5d2e6b" // Spinning Wheel
  ]
  Effect "7eceb9f7751d4634b572c8e236355104" // Rip
}

The repair blueprint consumes the same material type as the salvage output (Cloth or Leather) and requires a Spinning Wheel (RequiresNearbyCraftingTags). The repair operation is RepairTargetItem, which is the standard repair operation type for clothing items.

Dye blueprints (color variants)

Backpacks that have color variants (Daypack, Travelpack, Dufflebag) include an additional dye blueprint that converts the white base variant to a color variant. The dye blueprint requires the white backpack as a critical input, a dye consumable (Flare item matching the target color), and a Dye Vat crafting station.

{
  CategoryTag "ebe755533bdd42d1871c3ac66b89530f" // Apparel
  InputItems
  [
    {
      ID "c387f10875af49cda3afdfe0985b2767" // White Daypack
      Critical true
    }
    "2e3326e006904aae90aead15bcc2e8a3" // Blue Flare
  ]
  RequiresNearbyCraftingTags
  [
    "8e86b740dafc46f7bf98c5040c9b223e" // DyeVat
  ]
  OutputItems this
  Effect "61edeaee95b742a3a0b589f769261cdb" // DyeVatCraftingEffect
}

The dye pattern is important for mod authors who are producing a color-variant series of backpacks. The dye pattern uses the CategoryTag for the Apparel category (not Salvage or Repair), uses OutputItems this (producing the item whose .dat contains the blueprint), and requires Critical true on the base item input to prevent the player from substituting an incorrect variant.

Worked example: Custom Military Rucksack

The following worked example walks through authoring a complete backpack mod from scratch, using field values based on the shipped Alicepack and Pack_Spec_Ops configurations.

Asset.dat

ID 51001
GUID 3a6f8c1b9e2d4a7b5c0d8e3f6a1b4c9d
Type Backpack
Rarity Rare
Useable Clothing

Size_X 2
Size_Y 2
Size_Z 0.6

Width 7
Height 6

Blueprints
[
  {
    Name Salvage
    CategoryTag "7ed29f9101ae4523a3b2e389414b7bd9"
    InputItems this
    OutputItems "14901f32cd3240179fd6124324cc27e5 x 5"
    Effect "7eceb9f7751d4634b572c8e236355104"
  }
  {
    Name Repair
    CategoryTag "732ee6ffeb18418985cf4f9fde33dd11"
    Operation RepairTargetItem
    InputItems "14901f32cd3240179fd6124324cc27e5 x 5"
    RequiresNearbyCraftingTags
    [
      "2ac5ddc545a848008c0308d21f5d2e6b"
    ]
    Effect "7eceb9f7751d4634b572c8e236355104"
  }
]

English.dat

Name Custom Military Rucksack
Description Heavy-duty tactical rucksack with 42-slot storage capacity. Resistant to wear and tear. Can be repaired with cloth at a spinning wheel.

Field-by-field explanation

Field	Value	Rationale
ID	51001	In the 50000+ range to avoid vanilla collision.
GUID	Freshly generated	Never reuse GUIDs. This GUID was generated for this example only and must not be used in a published mod.
Type	Backpack	Assigns the item to the Backpack clothing slot.
Rarity	Rare	Indicates higher loot value. Standard backpacks use Uncommon; tactical packs use Rare.
Useable	Clothing	Mandatory for all wearable items.
Size_X / Size_Y	2 / 2	Standard backpack inventory footprint. Most shipped backpacks use 2x2.
Size_Z	0.6	Standard visual depth scale. Matches the Alicepack and Pack_Spec_Ops values.
Width	7	Horizontal grid count. 7 columns provides a balanced aspect ratio.
Height	6	Vertical grid count. 6 rows with 7 columns creates 42 slots - a mid-range capacity between the Daypack (28) and the Alicepack (56).
Blueprints	Salvage + Repair	Standard blueprint block following the shipped backpack pattern. Salvage yields 5 Cloth; Repair consumes 5 Cloth at a Spinning Wheel.

Testing the backpack in-game

1. Place the Asset.dat and English.dat in the mod folder: Workshop/Content/304930/<modID>/Items/CustomMilitaryRucksack/.
2. Place the master bundle in Workshop/Content/304930/<modID>/Bundles/.
3. Launch Unturned™ in single-player.
4. Spawn the backpack: @give 51001.
5. Open inventory. Confirm the backpack appears in the inventory with the correct icon.
6. Equip the backpack. Confirm the storage grid appears in the inventory UI (7 columns × 6 rows = 42 visible slots).
7. Place items into the backpack grid. Confirm items persist when the inventory is closed and reopened.
8. Unequip the backpack. Confirm the backpack grid is removed and items are moved to the base inventory.
9. Confirm the backpack prefab is visible on the character skeleton at the correct position and scale.
10. Test the salvage blueprint at a crafting station. Confirm salvage yields 5 Cloth.
11. Test the repair blueprint at a Spinning Wheel. Confirm a damaged backpack is restored to full condition.

Pro Backpack flag behavior

The Pro flag on backpack assets follows the same semantics as the Pro field on every other item type. When Pro is present (no value required - the field is a flag), the item is gated behind the player's PRO/Gold status. Non-PRO players cannot equip the backpack. They can see it in inventory, pick it up from the ground, and transfer it between storages, but they cannot put it on the Backpack slot.

The shipped game files show a clear split: backpacks that provide storage utility (Daypack, Travelpack, Dufflebag, Leather_Pack, Pack_Spec_Ops, Alicepack, Diving_Tank) do NOT carry the Pro flag. Backpacks that are purely cosmetic or vanity items (capes, shields, wings, instrument cases, quivers, tail items, novelty backpacks) carry the Pro flag and lack Width and Height fields entirely. The distinction is intentional: storage-providing backpacks are functional items available to all players; cosmetic backpacks are PRO-tier rewards or purchasable vanity items.

Category	Has Width/Height	Has Pro flag	Example items
Functional backpack	Yes	No	Alicepack, Daypack, Travelpack, Dufflebag, Leather Pack
PRO cosmetic backpack	No	Yes	Wings, Cape, Skateboard, Harp, Quiver, Tail items
PRO functional (rare)	Yes (8x5)	Yes	None observed in shipped set - this combination does not appear

Backpack field presence analysis from shipped game files

The following table documents every .dat field observed across the 50+ shipped backpack items examined for this article, with the percentage of items that include each field.

Field	Presence rate	Typical value(s)	Notes
GUID	100%	32-hex-digit GUID	Every backpack has a unique GUID.
Type Backpack	100%	Backpack	All items in the Backpacks folder use Type Backpack.
ID	100%	Varies (9 to 1771)	Vanilla IDs range from 9 (Daypack_Red) to 1771 (Turtle_Backpack).
Size_X / Size_Y	80%	2 / 2	Most backpacks use 2x2. Wings uses 3x2. Squid_Backpack omits Size_X/Y.
Size_Z	80%	0.35-1.6	Present on most but not all backpacks. Squid_Backpack uses 0.35; Wings uses 1.6.
Pro	60%	flag	Present on all vanity/cosmetic backpacks. Absent on functional storage backpacks.
Useable Clothing	40%	Clothing	Present on functional backpacks with Width/Height fields. Absent on Pro vanity backpacks.
Width / Height	30%	Various	Present only on backpacks that provide storage expansion.
Blueprints	20%	Salvage + Repair	Present on functional backpacks. Absent on Pro vanity backpacks.
Rarity	20%	Rare, Epic, Legendary	Present on some functional backpacks and some vanity backpacks. Most omits this field.
Bypass_ID_Limit	4%	flag	Present only on HeadlessCape and Squid_Backpack.
Proof_Water	2%	flag	Present only on Diving_Tank.
Ignore_NPOT	2%	flag	Present only on Carpat_Lastman_Backpack.
Armor	0%	Not present	Backpacks do not provide armor in the shipped asset set. The SDG documentation confirms Armor has no effect on backpacks.

The presence analysis confirms that backpack .dat files are minimal compared to gun or magazine assets. A functional backpack with storage requires approximately 10 lines of configuration plus the optional Blueprints block.

Diagnostic table

Symptom	Most likely cause	Resolution
Backpack does not appear in inventory after @give	ID conflict or folder path incorrect	Confirm ID is unique; confirm folder path matches mod structure
Backpack appears but cannot be equipped	Useable Clothing missing from .dat	Add Useable Clothing field
Backpack equips but no storage grid appears	Width and Height fields missing or set to 0	Add Width and Height with positive values
Storage grid is smaller than expected	Width or Height set too low	Increase the dimension to match design intent
Storage grid does not appear in correct slot	Type is not Backpack	Change Type to Backpack
Backpack is invisible when equipped	Prefab not in bundle or prefab name mismatch	Confirm prefab exists in bundle with matching name
Pink material on backpack	Shader or material not assigned	Assign material in Unity prefab and rebuild bundle
Backpack clips through character model	Size_Z too large or mesh not fitted to skeleton	Reduce Size_Z or re-fit mesh to character skeleton
Non-PRO player cannot equip backpack	Pro flag present on a functional backpack	Remove Pro flag from the .dat
Backpack cannot be salvaged	Blueprints block missing	Add the standard Salvage blueprint block
Backpack cannot be repaired	Repair blueprint missing	Add the standard Repair blueprint block
Backpack items lost on unequip	Base inventory was full	Document the behavior to players in workshop description
Storage grid UI clips off-screen	Width > 10 or Height > 8	Reduce grid dimensions within the cohort-recommended bounds
Dye blueprint does not show up	CategoryTag is not Apparel or input GUIDs are wrong	Confirm the category tag and input item GUIDs match the actual items

Best practices

• Generate a fresh GUID for every backpack asset. Never reuse GUIDs from other items.
• Choose IDs in the 50000+ range to avoid collision with vanilla items (IDs 9-1771) and established community mods.
• Set Width and Height to match the intended capacity. Standard capacities: 16-28 (civilian pack), 30-40 (military pack), 48-64 (expedition pack).
• Author Size_Z values between 0.4 and 1.0 for standard backpacks. Test the visual depth in-game to confirm the mesh does not clip through the character's back or shoulders.
• Include salvage and repair blueprints for functional backpacks. The player community expects to be able to break down and repair storage items.
• Omit the Pro flag on functional backpacks. Reserve the Pro flag for cosmetic-only vanity backpacks.
• Write a descriptive English.dat entry that communicates the backpack's slot count. Players should know how much storage they are getting before equipping the item.
• Author the backpack prefab mesh to match the character skeleton. Use the vanilla character FBX as a reference to avoid z-fighting and clipping.
• Test with a full inventory before publishing. Unequipping a full backpack at the wrong moment is a data-loss risk that players should know about.
• Match the grid aspect ratio to the backpack's visual shape for intuitive inventory layout.

Frequently asked questions

Can a backpack have both storage and the Pro flag?

Yes, technically. The engine does not prevent combining Width/Height with the Pro flag. However, the shipped game files show zero instances of this combination. Functional backpacks (those with storage) do not carry the Pro flag; cosmetic backpacks (those with the Pro flag) do not have Width/Height fields. The cohort recommendation is to follow the shipped pattern: functional backpacks for all players, cosmetic backpacks for the PRO economy.

Is there a maximum storage size for backpacks?

The Width and Height fields are uint8 values, so the theoretical maximum is 255 × 255 = 65,025 slots. The practical maximum is constrained by the inventory UI. Grids wider than 10 columns or taller than 8 rows clip outside the inventory panel on standard player screen resolutions. The 57 Studios cohort recommendation is to stay within 10 × 8 for any backpack intended for public use.

Can a backpack provide armor?

No. The SDG documentation explicitly states that the Armor field (inherited from ItemClothingAsset) "does not cover any body part(s) when worn, so this property has no effect" on backpack items. Armor reduction on a backpack would be silently ignored by the engine. Add armor through the Vest slot or through Shirt/Pants items instead.

How does backpack storage interact with vehicle trunk storage?

Backpack storage and vehicle trunk storage are independent systems. Items stored in a backpack remain in the backpack when the player enters a vehicle. The backpack storage grid is not merged with the vehicle trunk grid. When the player exits the vehicle, the backpack storage is still intact and accessible.

What happens when a player dies while wearing a backpack?

On death, the backpack item and all items within its storage grid are dropped as loot at the player's death location. The backpack's contents are not returned to the player on respawn. This follows the standard Unturned™ death-drop behavior for all inventory items. Players should consider the death-drop behavior when deciding which items to carry in a backpack versus base storage.

Can I author a backpack that stores more items than the UI can display?

Yes, but the grid will extend beyond the visible area, requiring the player to scroll or resize the inventory panel. This is a poor user experience for public mods. The cohort recommendation is to limit storage grids to the UI-visible bounds of 10 × 8. If your design requires more than 80 slots, consider creating a placeable container (crate, locker) instead of a backpack.

Does the Size_Z field affect collision detection?

No. Size_Z is a visual depth scaling parameter only. It does not affect the player's hitbox, the backpack's collision shape, or the storage grid. A Size_Z value of 3.0 would make the backpack visually enormous on the character's back but would not change any gameplay behavior.

Can a backpack be placed in the world as a container?

No. Backpacks are Clothing-type items, not Storage-type items. They cannot be placed in the world as interactable containers. When a player drops a backpack from their inventory, it appears as a world item (a pickup, not an openable container). Items inside the backpack at the time of dropping are dropped as individual world pickups alongside the backpack item. If you need a placeable container, author a Storage-type item instead.

How do I make a backpack that requires a specific material to craft?

Add a craft blueprint (not a Salvage or Repair blueprint) to the Blueprints block. The Leather Pack (ID 1014) is the shipped example of a craftable backpack: it has a blueprint with CategoryTag "ebe755533bdd42d1871c3ac66b89530f" (Apparel), InputItems "01ee4903b12b4998aa0ad5d7a0a567ba x 3" (3 Leather), and RequiresNearbyCraftingTags for a Spinning Wheel. The craft blueprint is separate from the Salvage and Repair blueprints; a backpack can have all three blueprint types simultaneously.

Can I make a backpack that is compatible with a specific server role or faction?

Backpack assets do not have native role-based or faction-based access control. All players can equip any backpack that is not flagged as PRO. Role-based or faction-based backpack restrictions must be enforced at the server level through a plugin (OpenMod or RocketMod). The .dat file has no fields for role gating, group gating, or faction gating. If your RP server design requires faction-specific backpacks, enforce the restriction server-side and author the backpack .dat as a standard item.

Advanced considerations

Backpack inventory audio field override

The SDG documentation notes that the InventoryAudio field (inherited from ItemAsset) defaults to different sound effects based on backpack size. When Width or Height is less than 3, the engine defaults to Sounds/Inventory/LightMetalEquipment.asset. When either dimension is between 3 and 6, the engine uses Sounds/Inventory/MediumMetalEquipment.asset. When either dimension is 6 or greater, the engine uses Sounds/Inventory/HeavyMetalEquipment.asset. Mod authors can override this by explicitly setting the InventoryAudio field in the .dat, though the shipped backpacks in the vanilla set do not do so.

Cosmetic-only backpack pattern (the "cape/shield/wings" template)

The cosmetics-only backpack pattern - items that occupy the Backpack slot but provide no storage - is a common authoring scenario for RP servers. These items use a minimal .dat with identity fields and the Pro flag, plus Size_Z for visual depth tuning. They omit Width, Height, Useable Clothing, and Blueprints entirely. The cosmetics-only backpack acts as a visual attachment to the character skeleton without affecting inventory capacity.

Example cosmetics-only .dat (following the Cape pattern from the shipped files):

GUID <fresh-guid>
Type Backpack
ID 52001

Size_X 2
Size_Y 2
Size_Z 0.8

Pro

The cosmetics-only backpack requires no storage fields, no blueprints, and no Useable Clothing declaration. The Pro flag restricts equipping to PRO players; removing the flag makes it equippable by all players.

Backpack prefab authoring for the character skeleton

The backpack prefab uses the same SkinnedMeshRenderer and character skeleton binding as all other clothing items. The backpack binds to the Character_Spine1 and Character_Spine2 bones, with visual extension to the Character_LeftUpperArm and Character_RightUpperArm for shoulder straps. The prefab mesh should sit approximately 5-10 cm behind the character's back surface to avoid z-fighting with the back of the shirt or vest mesh.

The prefab hierarchy for a standard backpack:

MyBackpackPrefab (root, with no script component)
└── BackpackBody (SkinnedMeshRenderer)
    └── Mesh: Backpack geometry
    └── Material: Standard shader with textures
    └── Bones: Character_Spine1, Character_Spine2
    └── Root Bone: Character_Spine1

No animator component is needed for a backpack. The backpack does not have animation states; it deforms with the character skeleton.

Appendix A: Backpack .dat field quick reference

Field	Type	Required	Default	Source class
ID	uint16	Yes	-	ItemAsset
GUID	uint128	Yes	-	ItemAsset
Type	enum (Backpack)	Yes	-	ItemClothingAsset
Name	string	Yes	-	ItemAsset
Rarity	enum	No	Common	ItemAsset
Useable	enum (Clothing)	Yes	-	ItemClothingAsset
Size_X	uint8	Yes	-	ItemAsset
Size_Y	uint8	Yes	-	ItemAsset
Size_Z	float	No	1.0	ItemAsset
Width	uint8	No (functional packs)	0	ItemBagAsset
Height	uint8	No (functional packs)	0	ItemBagAsset
Pro	flag	No	not set	ItemAsset
Bypass_ID_Limit	flag	No	not set	ItemAsset
Proof_Water	flag	No	not set	ItemClothingAsset
Ignore_NPOT	flag	No	not set	ItemAsset
Armor	float	No	1.0 (no effect)	ItemClothingAsset

Appendix B: Backpack storage capacity comparison table

The following table compares vanilla backpacks by their storage capacity and loot utility. Values are taken directly from the shipped game files.

Backpack name	Vanilla ID	Width	Height	Slots	Rarity	Pro	Has blueprints
Daypack (all colors)	200-206	7	4	28	Not set	No	Yes (Salvage + Repair + Dye)
Travelpack (all colors)	245-252	5	7	35	Not set	No	Yes (Salvage + Repair + Dye)
Dufflebag (all colors)	1182-1189	7	4	28	Not set	No	Yes (Salvage + Repair + Dye)
Leather Pack	1014	6	5	30	Not set	No	Yes (Craft + Salvage + Repair)
Pack_Spec_Ops	1170	8	5	40	Legendary	No	Yes (Salvage + Repair)
Alicepack	253	8	7	56	Epic	No	Yes (Salvage + Repair)
Alicepack_Arctic	1511	8	7	56	Epic	No	Yes (Salvage + Repair)
Diving Tank	1178	2	4	8	Rare	No	Yes (Salvage + Repair)
Squid_Backpack	787	N/A	N/A	0	Epic	Yes	No
Wings	837	N/A	N/A	0	Not set	Yes	No
All capes and shields	562-957	N/A	N/A	0	Not set	Yes	No

The 40-slot Pack_Spec_Ops (Legendary) and the 56-slot Alicepack (Epic) are the largest functional backpacks in the shipped set. The Alicepack is considered the endgame storage backpack in vanilla survival gameplay.

Appendix C: External references

• Smartly Dressed Games modding documentation - Item assets - the official field reference for all item types including backpack and bag assets.
• Unturned on Steam - the Unturned™ store page and community hub.
• Clothing Asset Reference - the companion article that covers the Backpack slot assignment and the full clothing field set.
• Storage Asset Reference - covers the wearable container system and the common grid math shared between backpacks and placeable containers.
• Bag Asset Reference - the next article in this series; documents the ItemBagAsset base class that backpacks inherit from.
• Item Asset Anatomy - the shared field reference for all item types.
• Project Folder Structure and GUIDs - GUID generation and folder layout for all item mods.
• Master Bundle Export - the Unity bundling workflow used to package backpack prefabs.

Document history

Version	Date	Author	Notes
1.0	2026-07-26	57 Studios	Initial publication. Complete backpack .dat field reference, game-file evidence analysis, storage grid reference, blueprint system, worked example, FAQ, appendices.

Cross-references

• Clothing Asset Reference - the clothing article that covers the Backpack slot, slot enum, and the shared wearable field set.
• Storage Asset Reference - covers the wearable container field reference and the grid math shared with backpacks.
• Bag Asset Reference - the next article; documents the ItemBagAsset base class that provides Width and Height to backpack assets.
• Cloud Asset Reference - the previous article in this section.
• Item Asset Anatomy - the universal shared field reference for every item type.
• Project Folder Structure and GUIDs - GUID generation and folder layout conventions.
• Master Bundle Export - the Unity bundling pipeline for packaging prefabs.
• Smartly Dressed Games modding documentation - the official field reference for all item types.
• Unturned on Steam - game page and community.