This is the Switch equivalent of 3DS exheader. This is the file with extension ".npdm" in {Switch ExeFS}. The size of this file varies.

ACID

Offset	Size	Description
0	0x100	RSA-2048 signature
0x100	0x100	RSA-2048 public key
0x200	0x4	Magic "ACID".
0x204	0x8	Zeroes
0x20C	0x4	Format version? (1)
0x210	0x8	Title id
0x218	0x8	Title id again
0x220	0x4	#FS Access Control offset
0x224	0x4	#FS Access Control size
0x228	0x4	#Service Access Control offset
0x22C	0x4	#Service Access Control size
0x230	4	#Kernel Access Control offset
0x234	4	#Kernel Access Control size
0x238	0x8	Padding

ACI0

Looks like an old crappy version of ACID. It has the guessed version field 0 instead of 1.

Word	Bit	Description
0		Version? Always 1.
1	0	MountContent* is accessible when set.
0	3	This is only bit set for ShopN in the permissions-u32.

This is a list of service-name strings which the title has access to, with the following structure:

 +0: control_byte
 +1: {service-name without nul-terminator}

Bitmask 0x0F in control_byte is the {length of the service-name without nul-terminator} - 1.

Bitmask 0x80 in control_byte means service is allowed to be registered.

The service string can contain a wildcard * character.

On Switch, descriptors are identified by pattern 01..11 in low bits.

Pattern of bits 15-0	Type	Fields
`0bxxxxxxxxxxxx0111`	Kernel flags	?
`0bxxxxxxxxxxx01111`	Syscall mask	Bits 29-31: Syscall mask table index; Bits 5-28: mask
`0bxxxxxxxxx0111111`	Map IO page	Bits 7-31: page
`0bxxxxxxxx01111111`	Map IO range	Bits 7-31: page then size alternating
`0bxxxxx11111111111`	Interrupt pair	Bits 12-21: irq0, bits 20-31: irq1, 0x3FF means empty.