Human-readable companion to structure.bt (the 010 Editor binary template authored by Twilight). The .bt file is the byte-exact oracle — when the two ever disagree, the .bt wins and this document is wrong. This page exists so the layout can be read, reviewed, and cross-referenced (it is the offset oracle the test suite is written against) without opening 010 Editor.

A Pokémon Red/Blue save (.sav) is exactly 32 KiB (0x8000 bytes) — a verbatim dump of the cartridge's battery-backed SRAM. It is divided into four 8 KiB (0x2000) banks.

Bank	File range	Contents
Bank 0	0x0000–0x1FFF	Hall of Fame records + sprite/scratch buffers
Bank 1	0x2000–0x3FFF	Main data — the live game state (player, party, current box, world)
Bank 2	0x4000–0x5FFF	PC storage Boxes 1–6 + their checksums
Bank 3	0x6000–0x7FFF	PC storage Boxes 7–12 + their checksums

Memory ↔ SAV address conversion

The Main Data block in Bank 1 is a byte-for-byte image of the game's working RAM (WRAM). To convert between an in-game WRAM address and its file offset:

file_offset = wram_addr - 0xAD54 (convert from memory to SAV)

wram_addr = file_offset + 0xAD54 (convert from SAV to memory)

For example Main Data begins at file 0x25A3, which is WRAM 0xD2F7 (wPokedexOwned).

Bank 0 — Hall of Fame & scratch (0x0000–0x1FFF)

Offset	Size	Field	Notes
0x0000	0x188	Sprite buffer 0	Decompression/scratch space, not meaningful in a saved file
0x0188	0x188	Sprite buffer 1
0x0310	0x188	Sprite buffer 2
0x0498	0x100	Unused
0x0598	50 × HOF_RECORD	Hall of Fame	50 records, 6 mons each (see HOF_RECORD)
—	0x7A8	Unused	Pads out to the end of the bank

HOF_RECORD_POKEMON is species(1) + level(1) + name(0xB) + padding(0x3) = 16 bytes; HOF_RECORD is 6 of them.

Bank 1 — Main data (0x2000–0x3FFF)

Offset	Size	Field
0x2000	0x598	Unused
0x2598	0xB	Player name (terminated Gen-1 text)
0x25A3	…	Main Data block (table below)

Main Data block (begins 0x25A3 = WRAM 0xD2F7)

The block follows the WRAM layout exactly, so each field's WRAM address is file_offset + 0xAD54. Key verified offsets:

File offset	WRAM	Size	Field	Notes
0x25A3	0xD2F7	19	Pokédex owned	Bitfield, 151 species + 1 unused bit (POKEDEX_BITS)
0x25B6	0xD30A	19	Pokédex seen	Same bitfield layout
0x25C9	0xD31D	42	Bag items	count(1) + 20×{id,qty} + terminator(1)
0x25F3	0xD347	3	Money	3-byte big-endian BCD
0x25F6	0xD34A	11	Rival name
0x2601	0xD355	1	Options	Text speed / battle style / battle animation bits
0x2602	0xD356	1	Badges	8 badge bits (Boulder…Earth)
0x2604	0xD358	1	Letter delay flags
0x2605	0xD359	2	Player ID	Trainer ID

After the header above, Main Data continues (in this order; see .bt for exact field sizes) with the Map / overworld state block (MAP: music, current map, coordinates, tileset, connections, warps, signs, sprite movement data), the PC box items list (count + 50×{id,qty} + terminator), the current-box index (CUR_BOX: 7-bit box number

"don't format" flag), HOF record count, slot-machine coins (2 bytes BCD), the missable-objects bitfield + list, the large game-progress event flags (GAME_PROG), owned hidden items/coins, the player movement mode (walk/bike/surf), towns visited, safari steps, fossil state, a long run of VARIOUS_FLAGS1–8 and DEFEATED_GYMS bitfields, the 320-byte completed-game-events array, the enemy/grass-encounter scratch unions, play time, Safari Zone state, and the Daycare record (dayCareInUse + name + OT + BOX_MON).

Sprite, party, and current-box sections (still Bank 1)

Section	Contents
SPRITE_DATA_SEC	Player + 15 overworld sprites (SPRITE_DATA_ENTRY) and their extra data (SPRITE_DATA_EXTRA_ENTRY)
PARTY_DATA_SEC	partyCount(1) + 6 species bytes + terminator, then 6 × PARTY_MON, then party OT names and nicknames
BOX_DATA_SEC	The current box working copy (same layout as a stored box, below)

Bank 1 trailer

Field	Notes
Tileset type	1 byte
Main data checksum	1 byte at file 0x3523 — 8-bit checksum over the Main Data region (0x2598–0x3522). The editor recomputes this on save; it does not reject a file with a bad one.
Unused	0xADC bytes padding to 0x3FFF

Banks 2 & 3 — PC storage boxes

Each bank holds six boxes as BOX_DATA_SEC, followed by checksum bytes and padding.

	Bank 2	Bank 3
Boxes	1–6	7–12
Box data	0x4000–0x5A4B (6 × 0x462)	0x6000–0x7A4B
All-boxes checksum	0x5A4C	0x7A4C
Per-box checksums (6)	0x5A4D–0x5A52	0x7A4D–0x7A52
Unused	0x5AD bytes to 0x5FFF	0x5AD bytes to 0x7FFF

The bank-2 all-boxes checksum lives at 0x5A4C over range 0x1A4C (6 boxes × 0x462). Getting this off by one corrupts Box 6's last data byte — see notes/reference/fix-patterns.md.

BOX_DATA_SEC (one box = 0x462 = 1122 bytes)

Size	Field
1	Count (number of mons in the box)
21	Species list (terminated)
20 × 33	20 × BOX_MON (33 bytes each)
20 × 11	Original-trainer names
20 × 11	Nicknames

Reusable record types

BOX_MON (33 bytes) — a stored Pokémon

species(1), hp(2), boxLevel(1), status(1), type1(1), type2(1), catchRate(1), moves(4), originalTrainer(2), exp(3), hpExp(2), attackExp(2), defenseExp(2), speedExp(2), specialExp(2), IV(2), PP(4).

IV packs four 4-bit nibbles: attack, defense, speed, special (HP IV is derived from the parity of the others).
PP is, per move, a 6-bit current-PP value + a 2-bit PP-Up count.

PARTY_MON (44 bytes) — a party Pokémon

A BOX_MON plus the battle-ready computed stats: level(1), maxHP(2), attack(2), defense(2), speed(2), special(2).

Other small records

ITEM_LIST_ENTRY — { id, amount } (2 bytes); item lists are count + N×entry + 0xFF terminator.
INDEX_LIST_ENTRY — { id, index } (2 bytes).
WARP_ENTRY — { y, x, destWarp, destMap } (4 bytes).
POKEDEX_BITS — 152 single-bit flags (151 species + 1 unused), 19 bytes, least-significant-bit-first by national dex order.