Pokémon 3rd Generation

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The third generation Pokémon games are comprised of Ruby, Sapphire, Emerald, FireRed and LeafGreen. Since all five share a common set of data structures with only some offsets and minor details in difference, it seems more effective to consider them one single "game" and note the differences where applicable.

Notable ROM data offsets

Description Fire Red Ruby Notes
Battle sprites $2350AC $1E8354 Pointer tables are in system order.
Monster heights $235E6C Unknown N/A
Battle back sprites $23654C $1E97F4 Pointer tables are in system order.
Battle sprite palettes $23730C $1EA5b4 N/A
Battle sprite shiny palettes $2380CC $1EB374 N/A
Trainer sprites $23957C $1EC53C Offset is a pointer table.
Trainer palettes $239A1C $1EC7D4 N/A
Trainer Class names $23E558 $1F0208 N/A
Trainer data $23EAF1 $1F0525 N/A
Pokémon Species names $245EE0 $1F7184 Names are listed in system order.
Move names $247094 $1F8320 N/A
Ability names $24FC4D $1FA26D
Move data $250C04 $1FB12C Data is stored in the same order as the move names.
TM allowance sets $252BC8 $1FD0F0 N/A
Pokémon base stats $254784 $1FEC30 Stats are listed in system order.
Move sets $257496 $20192A N/A
Evolution chains $25977C $203B90 N/A
Pokémon Party/box sprites $3D37A0 $3BBD20

Offset points to a pointer table.

Data is in system order.

Party icon palette $3D3740 $E966D8 N/A
Party icon palette LUT $3D3E80 $3BC400 Simple byte array
Item data $3DB028 $3C5580 N/A
TM-to-Move table $45A5A4 $376504 Maps TM numbers to moves
Pokédex data $44E850 $3B1874 Pokédex data is in National Dex order.
Footprints $43FAB0 $3B4EE4 Offset points to a pointer table
Contest data N/A $3C9408 N/A
Cries $48C914 $452590 M4A Voice Group-style pointer list. In system order?

Following the Pokémon image pointers, you may notice that each species has all its image data in one chunk.

More information on the data structures can be found at Bulbapedia: Category:Structures


Trainer and monster images are LZ77-compressed 64 by 64 pixels, 16 colors. Trainers' back-facing images are much taller and (in FireRed/LeafGreen) uncompressed. Monster front images in Emerald are 128 pixels tall to allow animation. In all games, certain monsters always have nonstandard heights (i.e. Castform). Alternate colors (aka shiny) are usually represented by the back-facing images since it makes an intuitive kind of sense.


Maps are split among banks, each bank roughly being one location. For example, there is a bank with all the cities and routes and several banks with each city's interiors. Generally, a map can be defined by a Doom-like "bank X, map Y" scheme. In FireRed, the bank pointer list is at $3526A8. Following one of the pointers found there yields that bank's map pointer list, which can be followed to a given map's header. Here is the map header format, including example data from Pallet Town (B3M0, 0x350618):

Byte order Data type Description Example
Pointer Map data 0x082DD4C0
Pointer Event data 0x083B4E50
Pointer Map scripts 0x0816545A
Pointer Connections 0x0835276C
Little endian Short Music index 0x012C (Pallet Town)
Little endian Short Map pointer index? 0x004E
Byte Label index 0x58 ("Pallet Town")
Byte Visibility (i.e HM Flash) 0x00
Byte Weather 0x02
Byte Map type (City? Village? etc) 0x01
Little endian Short ??? 0x0601
Byte Show label on entry 0
Byte In-battle field model id 0

The map layout data is another header:

Byte order Data type Description Example
Little endian Integer Width in tiles 24
Little endian Integer Height in tiles 20
Pointer Border 0x082DD0F8
Pointer Map data / Tile structure 0x082DD100
Pointer Global tileset 0x082D4A94 (outside)
Pointer Local tileset 0x082D4AAC
Byte Border width 2
Byte Border height 2

Border size is only in FireRed/LeafGreen. In R/S/E it is missing and borders are always 2x2 squares.

Map data is quite straightforward: each 16-bit entry encodes the tile number and attribute. The trick is that there are only 64 attributes and 512 tiles, so the 16-bit entry is split up 6:10 instead of 8:8 for Ruby, Fire Red, and additionally Emerald. The border data is the same format and includes data although it may or may not be used by the game.

TilesetHeader is stored in the following format:

Byte order Data type Description Example
Byte Compressed 0/1 0x1
Byte Is primary 0/1 0x0
Byte Unknown  ?
Byte Unknown  ?
Little endian Integer Pointer to tileset image 0x08EA1D68
Little endian Integer Pointer to color palettes 0x08EA1B68
Little endian Integer Pointer to blocks 0x0829F6C8
Little endian Integer Pointer to animation routine (only if exist, else null) 0x08070155
Little endian Integer Pointer to behavior and background bytes 0x082A1EC8

Connection data is stored in the following format:

Byte order Data type Description Example
Little endian Integer Amount of map connections 0x2
Little endian Integer Pointer to connection data 0x0835276C

The actual connection data is formatted in sequence in this format for each connection:

Byte order Data type Description Example
Little endian Integer Connection direction 0x2
Little endian Integer Offset (In reference to connecting map) 0x0
Byte Map Bank 0x3
Byte Map Number 0x14
Little endian Short Filler 0x0000

Connection directions are either 0x0 for no connection, 0x1 for Down, 0x2 for Up, 0x3 for Left, 0x4 for Right, 0x5 for Dive, or 0x6 for Emerge. Dive and Emerge connections are valid in Fire Red but do not work without custom ASM for the proper tiles.