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W3M / W3X — Map Container Format

A .w3m (Reign of Chaos) or .w3x (Frozen Throne) file is a standard MPQ archive preceded by a 512-byte header and optionally followed by a 260-byte footer.

Header (fixed 512 bytes)

char[4]  file ID           must be "HM3W"
int      unknown           (often 0)
string   map name          null-terminated
int      map flags         (same flags as in war3map.w3i — see below)
int      max number of players
[padding with 0x00 bytes to fill the remaining 512 bytes]

Map flags (header + w3i)

Bit Value Meaning
0 0x0001 Hide minimap in preview screens
1 0x0002 Modify ally priorities
2 0x0004 Melee map
3 0x0008 Playable area was large, never reduced to medium
4 0x0010 Masked areas are partially visible
5 0x0020 Fixed player settings for custom forces
6 0x0040 Use custom forces
7 0x0080 Use custom tech tree
8 0x0100 Use custom abilities
9 0x0200 Use custom upgrades
10 0x0400 Map properties menu opened at least once
11 0x0800 Show water waves on cliff shores
12 0x1000 Show water waves on rolling shores 
char[4]   footer sign ID   "NGIS"  (= "sign" reversed)
byte[256] authentication data

Present only on official Blizzard-signed maps. Purpose/algorithm not publicly documented.

MPQ contents

Files that may appear inside the map archive:

(listfile)              MPQ filename list
(signature)             optional digital signature
(attributes)            optional CRC/timestamps
war3map.w3e             terrain
war3map.w3i             map info
war3map.wtg             GUI triggers
war3map.wct             custom text (JASS) triggers
war3map.wts             trigger strings
war3map.j               JASS2 main script
war3map.shd             shadow map
war3mapMap.blp          minimap image (BLP)
war3mapMap.b00          minimap image (alternate)
war3mapMap.tga          minimap image (TGA)
war3mapPreview.tga      loading screen preview
war3map.mmp             minimap icon positions
war3mapPath.tga         pathing map (old format, ≤1.21)
war3map.wpm             pathing map (new format, ≥1.30)
war3map.doo             doodads (trees, destructables)
war3mapUnits.doo        units and items
war3map.w3r             regions
war3map.w3c             cameras
war3map.w3s             sounds
war3map.w3u             unit object data (custom units)
war3map.w3t             item object data
war3map.w3a             ability object data
war3map.w3b             destructable object data
war3map.w3d             doodad object data
war3map.w3q             upgrade object data
war3mapMisc.txt         misc gameplay constants override
war3mapSkin.txt         skin/UI override
war3mapExtra.txt        extra data
war3map.imp             imported file list
war3mapImported\*.*     imported files (custom assets)

Notes for implementors

  • The MPQ starts at byte offset 512 (after the header).
  • To open a .w3x programmatically: skip the first 512 bytes, then parse as a standard MPQ.
  • The war3map.j may be relocated to Scripts\war3map.j by map protectors.
  • (listfile) is needed to enumerate files by name; some protected maps omit it.