Diablo II Item Format

for Diablo II v1.09 and the Diablo II Expansion Set: Lord of Destruction


Updated November 13, 2003
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Thanks for showing an interest in my Diablo II Item Format page.  While you're browsing, be sure to check out the preview of my game editor for unix+Motif.  I currently have the item editor in development!

Introduction

Having searched the web, I found very few references to the Diablo II .d2s file format, and most of them covered the old (pre-1.08) version.  Diablo II v1.09 has significantly changed the file format.  I have started another page which details the layout of the major parts of the .d2s file.  This document focuses specifically on the item structure -- all those pieces of the file tagged "JM".

Rather than describe everything in terms of byte offsets, I'm going to define the layout as a series of variable-length bit fields.  This is a critical part of the item format, because the position of many of the fields can change depending on what comes before it.  If I say a certain value is a 3-bit field starting at bit position 150, for example, this translates to bits 6 and 7 of the byte 18 and bit 0 of byte 19 in the data structure.  You can read an arbitrary bit field programatically using the following code (in C):

#define read_bits(start,size) \
    ((*((unsigned long *) &data[(start) / 8])
      >> ((start) & 7)) & ((1 << (size)) - 1))

Item List Header

An item list begins with the following simple header:

Byte Position SizeContents
0 2 chars Identifier string "JM" { 0x4a, 0x4d }
2 16 bits The number of items your character has.  This does not include gems or jewels which have been glued into socketed items.

Your item list ends with another 4-byte structure similar to the above, except the second field is zero (i.e., { 0x4a, 0x4d, 0, 0 }).

In the Expansion Set, your hireling has his/her own item list.  This list is separated from yours by the 2-character identifier "jf".  This is followed by an item list header for the hireling, and then his/her items.  The second item list is not terminated with the same 4-byte structure as the first; instead, it is followed by the 2-character identifier "kf".

Item Structure part 1: Simple Items

There are still many fields in the item structure which I haven't figured out yet, but I'll leave placeholders for them in case I find out what they mean in the future.  All sizes are in bits unless otherwise specified.

Bit Position SizeContents
02 chars Identifier string "JM" { 0x4a, 0x4d }
164 unknown
201 Item has been identified
216 unknown
271 Item is Socketed
281 unknown
291 This bit is set on items which you have picked up since the last time the game was saved.  Why?...
302 unknown
321
Item is a Player Ear
Thanks go to Mike of Denmark for identifying this bit.
331 "Newbie" item.  This bit is set on the weapon and shield your character is given when you start the game.  Apparently, this gives the item the property of having a repair cost of 1gp, as well as a sell value of 1gp.
343 unknown
371
Item is simple (only 111 bits {14 bytes} of item data)
Thanks go to Guillaume Courtin of France for discovering the meaning of this bit.
381 Item is Ethereal (Cannot be Repaired)
391 unknown; this bit is 1 on the items I've looked at
401 Item has been personalized (by Anya in Act V)
411 unknown
421 It looks like this bit indicates the item has been given a Rune Word.
4315 unknown; some of these bits may be set
583
Item location.  Actually, I have only seen a few values for these bits, so I'm not 100% certain of its validity.  If you see any other value here, let me know what it is and where the item is located.
0 Item is stored (see bit field 73)
1Item is equipped (somewhere on your body)
2Item is tucked in your belt (or sash)
4Item is being moved (i.e., has been picked up by the mouse).
6Item is glued into a socket.
614
If the item is equipped, this field tells where it is.  Possible values are:
1 head (helmet)
2neck (amulet)
3torso (armor)
4right hand (weapon)
5left hand (shield)
6right finger (ring)
7left finger (ring)
8waist (belt)
9feet (boots)
10hands (gloves)
11alternate right hand (Expansion Set only)
12alternate left hand (Expansion Set only)
654

Column number of the left corner of the item, counting from 0.  Your inventory has ten columns (numbered 0-9), your stash has six, and the Horadric Cube has four.

Note: Your belt is considered (for the purposes of the item format) to have no rows, but either 4, 8, 12, or 16 columns.  If you prefer, you can divide this field and use the 2 bits at position 67-68 for the row (but only for belts).

Note 2: If the item is equipped, glued to a socket, or in transit, then this field appears to contain old data from the last time the item was stored.  I.e., it may be non-zero, but the value is unused.

693

Row number of the top of the item, counting from 0.  Your inventory has four rows (numbered 0-3), your stash has four in normal characters or eight in Expansion Set characters, and the Horadric Cube has four.  (In the belt, this field is always zero.)

Note: If the item is equipped, tucked in your belt, glued to a socket, or in transit, then this field appears to contain old data from the last time the item was stored.  I.e., it may be non-zero, but the value is unused.

721 unknown
733
Actually, bit 74 seems to always be 0, but since bits 73 and 75 are related I just lump them all together.  If the item is neither equipped nor in your belt, this field tells where it is.  Possible values are:
0 not here (check bit field 58)
1inventory
4Horadric Cube
5stash
If you find an item having any other value in this field, let me know what the value is and the item's location!
76 4 chars
(8 bits ea.)
Item's type.  The type is 3 lower-case letters or numbers followed by a space; e.g., "amu " (Amulet) or "2hs " (Two-Handed Sword).  I have started a list of item identifiers (not posted; sorry), but it is by no means complete; I'm sure I don't even have half of what's out there!
Warning: This field is not byte-aligned!  it starts in the middle of byte 9 and runs to the middle of byte 13.
1083 The number of gems (or skulls or jewels) which have been glued to this item (if socketed).  There will be this many additional item structures for the gems immediately following this item, in the order that the gems were inserted.

Item Variant: Player Ears

The following information was provided by Mike of Denmark.

If the item is a Player Ear, its structure is slightly different than the Simple Items above. The last two fields in the Simple Item structure are replaced by the following:

Bit Position SizeContents
763 Character class of the ear's former owner.  The defined classes are:
     0  Amazon
     1  Sorceress
     2  Necromancer
     3  Paladin
     4  Barbarian
     5  Druid (Expansion character only)
     6  Assassin (Expansion character only)
797 Character level of the ear's former owner.
867 First character of the former owner's name.
937 × N-1 Second character of the former owner's name; Repeat until you get the whole name (15 characters maximum).
86 + 7 × N7 0  (this indicates the end of the name)

Following the end of the name, the rest of the final byte will be padded with 0's if necessary, and the Player Ear structure ends there.

Item Structure part 2: Extended Items

By "extended items" I mean any items which are not simple.  Simple items are those which need no further information than that given above--such as gems, potions, and small quest items--and their structure length is fixed at 14 bytes.  Everything else has an extended structure with a possibly variable length set of bit fields.  First, I'll describe the part of the structure that appears to be the same for all extended items.  From that point on, there will be no more "bit positions"; only "this field follows that field, if it exists".

Bit Position SizeContents
11132 Unique identifier.  Diablo II randomly generates a value for this field in order to discourage cheaters from "duping" items.  Supposedly, if it detects more than one extended item with the same unique ID, it will delete the duplicates.  (It hasn't done that for me in single player mode, though.)
1437
This appears to be the item's level; i.e., the level with which the item was created (or 'dropped').  The item level is based on the level of the monster who dropped it, the level of the area you're in if found in a chest, or, in rare cases, your characters level.  The item level determines what modifiers are allowed on the item.
Note: this is just a theory at this point, but it seems to hold for the items I've examined.
1504
Item quality.  This field can be one of the following values, which determines the quality-specific bit fields that follow:
1 low quality
2normal
3high quality
4magically enhanced
5part of a set
6rare
7unique
8crafted
Thanks go to Guillaume Courtin of France for finding the value of crafted items.

WARNING: DATA BELOW THIS POINT MAY CONTAIN ERRORS

Ring Data

After the above data, if the item is a ring, amulet, jewel, or charm, then it has a 1 bit followed by three more bits.  All other items (that I've seen) have just a single 0 bit.

SizeContents
1 If this bit is set, the item has one of multiple pictures associated with it; the next field determines which picture a particular item uses.  If this bit is 0, the next field is absent.  The picture field is used for rings, amulets, jewels, and charms.
3 Picture.  Optional; only present if the previous bit is 1.  This field chooses the particular graphic used to display the ring.

From this point on, my information is very iffy.

Unknown Field

SizeContents
1 This bit apparently is set for certain class-specific Expansion Set items.  It indicates the presence of the next 11-bit field.  If this bit is 0, the next field is absent.
11
Credit for the discovery of this field's meaning goes entirely to Guillaume Courtin of France.  Thanks! :->
This field indicates magic properties which are inherent in certain class-specific items.  A given class-specific item will (almost) always start with the same set of properties, even if its quality is "normal".  Other quality ratings may add more properties to the standard set.  It appears that items which will have this field are:
  • Amazon-only bows, spears, and javelins
  • Voodoo heads (Necromancer-only shields)
  • Paladin-only shields
  • Orbs (Sorceress-Only wands)

Low Quality Item Data

If the item is one of low quality, it has 3 more bits that give the quality details:

SizeContents
3
Quality:
0 Crude
1Cracked
2Damaged
3Low Quality
I haven't recorded any instances of other values, but that doesn't mean there won't be any.  Also, I'm certain the value has something to do with mods on an item's inherent (non-recorded) properties, such as weapon damage, but I haven't figured out yet what the correlation is.

Normal Item Data

Normal items have no extra quality data.

High Quality ("Superior") Item Data

If the item is one of high quality, it has 3 additional bits.

SizeContents
3unknown.  I'm certain the value has something to do with mods on an item's inherent (non-recorded) properties, such as weapon damage, but I haven't figured out yet what the correlation is.

Magically Enhanced Item Data

Magically enhanced items have two 11-bit fields representing the item's prefix and suffix.  Either one (but not both) may be omitted.  The prefix and suffix each are used in choosing the magical enhancements for an item (although the enhancements are modifiable), and can also increase the minimum level required to use them item and affect the item's color.


SizeContents
11 Item prefix (i.e., "Gold" or "Tangerine").  I've started a list of prefix identifiers, but it is very sparse at this time.  If this field is 0, the item has no prefix.
11 Item suffix (i.e., "of Greed" or "of Life").  I've started a list of suffix identifiers, but it is very sparse at this time.  If this field is 0, the item has no suffix.

Set Item Data

Set items have a 12-bit field containing the ID of the set.  (Not the set member, but the whole set.)  The set member is identified by cross-referencing the item type with the set ID.  Also note that set items have an extra field following the item-specific data.

SizeContents
12
Set identifier; i.e., all items which are part of the set will have the same value in this field.  Since I've only identified a few set items, I'll give their ID's here:
2 Cleglaw's Brace
3Iratha's Finery
4Isenhart's Armory
6Milabrega's Regalia
7Cathan's Traps
11Berserker's Arsenal
12Death's Disguise
13Angelic Raiment

Rare Item Data

This is by far the worst beast to decode.  Rare items have a variable number of bits before we get to the item contents, and this number can vary anywhere from 55 to 88!

Update 3/14/2002: EUREKA!!  I've finally figured out the variable fields!  See the table below.

SizeContents
8 This is the ID for the first word of the item's name (i.e., "Stone" or "Doom").
8 This is the ID for the second word of the item's name (i.e., "Finger" or "Shroud").
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 First magic prefix (optional).  Although this "prefix" isn't actually shown in the item name, it is used in determining the magical properties, required level, coloring, and other attributes of the rare item.
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 First magic suffix (optional).  Although this "suffix" isn't actually shown in the item name, it is used in determining the magical properties, required level, coloring, and other attributes of the rare item.
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Second magic prefix (optional)
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Second magic suffix (optional)
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Third magic prefix (optional)
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Third magic suffix (optional)

Unique Item Data

Unique items have an additional 12 bit field, which in most cases is the unique item ID.  The few exceptions are certain quest items (e.g., the Horadric Malus).

SizeContents
12
Item identifier.  Since I've only identified a few unique items, I'll give their ID's here:
13 Ume's Lament Grim Wand
31Hellplague Long Sword
75Wormskull Bone Helm
77Undead Crown Crown (no, that is not a typo!)
91Goldskin Full Plate Mail
120Nagelring Ring (not a typo either; I checked)
123Amulet of the Viper
125Horadric Staff
126Hell Forge Hammer
4095
(0xfff)
(other; probably a quest item)

Crafted Item Data

Crafted items appear to be coded exactly like rare items, having a rare name (two parts) and six optional prefixes / suffixes.

SizeContents
8 This is the ID for the first word of the item's name (i.e., "Stone" or "Doom").
8 This is the ID for the second word of the item's name (i.e., "Finger" or "Shroud").
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 First magic prefix (optional).  Although this "prefix" isn't actually shown in the item name, it is used in determining the magical properties, required level, coloring, and other attributes of the crafted item.
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 First magic suffix (optional).  Although this "suffix" isn't actually shown in the item name, it is used in determining the magical properties, required level, coloring, and other attributes of the crafted item.
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Second magic prefix (optional)
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Second magic suffix (optional)
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Third magic prefix (optional)
1 If this field is 1, the next 11-bit field is present.  If 0, the next field is absent.
11 Third magic suffix (optional)

Rune Word

If the item has a rune word (indicated by bit 42 being set), there is an additional field at this point.

SizeContents
12 This appears to be an index to the rune word, although I can't say what the index is based on.  The first rune word, "Ancient's Pledge", has a value of 27.  The next rune word, "Black", has a value of 32.  etc.
4 Unknown; the value is 5 on all items I've looked at.

Personalization

The following segment is present if and only if the item is personalized (i.e., bit 40 is set).  Only armor and weapons (except for quest items) can be personalized.

SizeContents
7First character of the owner's name (just plain ASCII!)
7Second character of the owner's name
7 × N-2Repeat until you get the whole name (15 characters maximum)
70  (this indicates the end of the name)

Unknown Field

All items have this field between the personalization (if it exists) and the item-specific data:

SizeContents
1unknown; this usually is 0, but is 1 on a Tome of Identify.  (It's still 0 on a Tome of Townportal.)

Item Structure part 3: Item-Specific Data

The presence of the following fields depends on the item type.  Fields which are present will be stored in the order shown.  Unfortunately there is no means of telling which fields are present from the item data itself; you need to look up the item type in a table to figure out whether it is a weapon, armor, or stack, and read the fields accordingly.

Armor: Defense Rating

SizeContents
10 Defense value + 10.  i.e., a defense rating of 23 would be stored in this field as 33; thus the maximum defense value you can store is 1013 (although I haven't tried it).  Note that this is the base defense rating, before applying any magical enhancements (i.e., the number shown in white).

Armor and Weapons: Durability

Even though stacked weapons don't show any durability rating in the game, they still have two 8-bit fields in the same spot.  This includes bombs (exploding and gas potions).  The values in such cases are very small, so I'm not sure what they mean.

SizeContents
8 Maximum Durability.  Note that this is the base durability, before applying any magical enhancements (i.e., the number shown in white).
Note: I've found an indestructable item, and it appears that in such a case the maximum durability field is zero!
8 Current Durability.  This may be greater than the maximum durability if the item is magically enhanced.
Note: I've found an indestructable item, and it appears that in such a case the current durability field is missing!

Armor and (non-stacked) Weapons: Sockets

The following field is present if and only if the item is socketed (i.e., bit 27 is set).

SizeContents
4Number of sockets
Note that even though this field is 4 bits wide, each item type has a built-in upper limit to the total number of sockets.  This limit is built into the game.  The most I've ever seen is 6 for, e.g., a gothic axe.

Tomes:

Tomes have an extra 5 bits inserted at this point.  I have no idea what purpose they serve.  It looks like the value is 0 on all of my tomes.

SizeContents
5unknown

Stacked Weapons, Quivers, Keys, and Tomes: Quantity

SizeContents
9Quantity

Item Structure part 3: Magical Enhancements

Item Structure part 2bis: Set Item Data Revisited

Items which are part of a set have an additional 5 bits following the item-specific data.

SizeContents
5 This appears to be an indicator of how many lists of magic properties follows.  The first list are the properties the item has if you do not have any other members of the set.  Following lists are applied once you equip other items in the set.  The value is 1 if there are two (total) property lists, or 3 if there are three property lists.

Following the item-specific data are a variable number of variable length bit fields describing any magical enhancements placed on the item.  Each property begins with a 9-bit identifier.  An identifier of 0x1ff (all 1's) indicates the end of the property list ... except in the event the item belongs to a set, in which case there will be another one or two groups of magical properties following, depending on whether the set item data (above) is 1 or 3, respectively.  Also, if an item has been given a Rune Word, it appears that the Rune Word's properties begin with a 0x1ff identifier (presumably to set them apart from the item's normal properties... but I need to examine more items to be certain.)

Because the number of bits (and fields) after the 9-bit identifier varies, I do not give a field width here.  Instead, check my table of magic properties for field sizes.  I'm sure it's not complete, but it does have most of the common properties.

Following the last 9-bit value of 0x1ff, the rest of the final byte will be padded with 0's if necessary, and the item structure ends there.  For example, if the item had 341 bits of data, the last (43rd) byte will be 0x1f.  If the item had 248 bits of data, the last (31st) byte will be 0xff.


Please send any additions or corrections to me using my web-based mail form.