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This page describes the format and encryption of extdata, "extra data" stored on [[SD_Filesystem|SD card]] and NAND.
This page describes the format and encryption of extdata, "extra data" stored on [[SD_Filesystem|SD card]] and [[Flash_Filesystem|NAND]].
At /Nintendo 3DS/<SomeID>/<SomeID>/extdata/<ExtdataIDHigh> on SD is directories for each title.(ExtdataIDHigh is always 00000000) Some titles have Quota.dat stored in these directories, not all titles use it. The dirname for these directories is the ExtdataIDLow. Then there's a sub-directory 00000000, which contains the actual extdata. Size and number of files in this dir varies per title.
At /Nintendo 3DS/<SomeID>/<SomeID>/extdata/<ExtdataID-High> on SD is directories for each title.(ExtdataID-High is always 00000000) Some titles can have Quota.dat stored in these directories. The directory-name for these directories is the ExtdataID-Low. Then there's a sub-directory 00000000, which contains the actual extdata. Size and number of files in this dir varies per title.
NAND stores the shared extdata and is structured exactly the same way, see [[Flash Filesystem]].
Regular apps can only mount SD/NAND extdata using the same extdataID which is stored in the [[NCCH#CXI|CXI]] exheader. Therefore, regular apps which have the exheader extdataID set to zero can't use extdata. This restriction doesn't apply for shared extdata with extdataID high bitmask 0x48000 stored on NAND. System apps with a certain access right can mount arbitrary extdata.
Regular apps can only mount SD extdata using the same extdataID which is stored in the [[NCCH#CXI|CXI]] exheader. Therefore, regular apps which have the exheader extdataID set to zero can't use extdata. This restriction doesn't apply for shared extdata with extdataID high bitmask 0x48000 stored on NAND. System apps with a certain access right can mount arbitrary extdata.
All NAND extdata is shared extdata, while all SD extdata is normal extdata. Thus, normal extdata doesn't exist on NAND, and shared extdata doesn't exist on SD. The extdataID high excluding that bitmask is always zero for shared extdata.
All NAND extdata is shared extdata, while all SD extdata is normal extdata. Thus, normal extdata doesn't exist on NAND, and shared extdata doesn't exist on SD. The extdataID high excluding that bitmask is always zero for shared extdata.
Most extdata uses the same FS as [[savegames]], except extdata uses [[Savegames|DIFF]] instead of DISA. However some extdata files are raw, without any FS.
Most extdata uses the same FS as [[savegames]], except extdata uses [[Savegames|DIFF]] instead of DISA. However some extdata files are raw, without any FS.
Quota.dat uses the same encryption as extdata, and seems to use the same FS as the actual extdata. It's unknown whether Quota.dat is used anymore on the latest system version at all.
Quota.dat uses the same encryption as extdata, and seems to use the same FS as the actual extdata. It's unknown what Quota.dat is used for.
'''QUOT'''
'''QUOT'''
When extdata is created, these are *always* created regardless of whether the title actually uses them.
When extdata is created, these are *always* created regardless of whether the title actually uses them.
User extdata and SpotPass extdata use separate mount points at /user and /boss. Therefore one mount can't access the other directory, and also can't access /icon.(The title's SpotPass extdata can be mounted by the title itself, if it uses SpotPass)
User extdata and SpotPass extdata use separate [[FS:OpenArchive|mount]] points at /user and /boss. Therefore one mount can't access the other directory, and also can't access /icon.(The title's SpotPass extdata can be mounted by the title itself, if it uses SpotPass)
* /icon This file contains the extdata [[SMDH|icon]] displayed in data management. This icon can only be written to by titles when creating extdata, titles would have to recreate extdata to change the icon. This file can't be read directly, instead it is read via [[FS:ReadExtSaveDataIcon]].
* /icon This file contains the extdata [[SMDH|icon]] displayed in data management. This icon can only be written to by titles when creating extdata, titles would have to recreate extdata to change the icon. This file can't be read directly, instead it is read via [[FS:ReadExtSaveDataIcon]].
| 00000217
| 00000217
| 00000227
| 00000227
| Mii Maker
| Mii Maker, likely contains an ExBanner
|-
|-
| 0000020d
| 0000020d
| 0000021d
| 0000021d
| 0000022d
| 0000022d
| Face Raiders
| Face Raiders, likely contains an ExBanner
|-
|-
| 00000200
| 00000200