NRO is the executable format for non-ExeFS binaries.

It starts with the NRO-start structure then the "NRO" header and mainly describes .text, .rodata, and .data segments (like a short-form of ELF program headers).

NroHeader

This is "nn::ro::detail::NroHeader".

Offset	Size	Description
0x0	0x10	Rocrt
0x10	0x4	Signature ("NRO0")
0x14	0x4	Version
0x18	0x4	Size (total NRO file size)
0x1C	0x4	Flags
0x20	0x4	TextMemoryOffset
0x24	0x4	TextSize
0x28	0x4	RoMemoryOffset
0x2C	0x4	RoSize
0x30	0x4	DataMemoryOffset
0x34	0x4	DataSize
0x38	0x4	BssSize
0x3C	0x4	Reserved
0x40	0x20	ModuleId
0x60	0x4	DsoHandleOffset
0x64	0x4	Reserved
0x68	0x4	EmbeddedOffset
0x6C	0x4	EmbeddedSize
0x70	0x4	DynStrOffset
0x74	0x4	DynStrSize
0x78	0x4	DynSymOffset
0x7C	0x4	DynSymSize

RocrtHeader

This is "nn::ro::detail::RocrtHeader".

Offset	Size	Description
0x0	[17.0.0+] 0xC ([1.0.0-16.1.0] 0x8)	ModuleHeaderLocation
0xC	0x4	Reserved

ModuleId

This is "nn::ro::detail::ModuleId".

Value of "build id" from ELF's GNU .note section. Contains variable sized digest, up to 32bytes.

Homebrew

Assets

This is an optional custom assets section for homebrew, this is located at file offset {NroHeader.size}. See also switch-tools for implementation.

The below offsets are relative to the beginning of the assets section (AssetHeader).

AssetHeader

Offset	Size	Description
0x0	0x4	Magic "ASET"
0x4	0x4	Format version, currently 0.
0x8	0x10	AssetSection icon. Used by the Homebrew Launcher. Like official icons, this is a 256x256 JPEG.
0x18	0x10	AssetSection NACP. Used by the Homebrew Launcher.
0x28	0x10	AssetSection romfs. Can be used by the application.

AssetSection

Offset	Size	Description
0x0	0x8	Offset
0x8	0x8	Size, 0 indicates this section is empty.