The Home Menu is the heart of the Nintendo 3DS. From there one can start games, applications, and access various processes including the friends list. It is launched by NS, and is always running in the background in 3DS-mode except when other programID-high 00040030 applications like Internet Browser, Friend-List, etc are running. Home Menu is still running while System Settings is running, however the System Settings application does not allow directly returning to home-menu. The system will normally re-launch Home Menu when the Home Menu process crashes/terminates. When this re-launch occurs while Home Menu is active, Home Menu displays an error message which says to manually reboot the system.
 System Versions
Nintendo devised a system, whereby updates would be delivered via two channels:
- Card Updates (CUP) - The Nintendo 3DS is updated with data from an update partition on retail gamecard title.
- Network Updates (NUP) - The Nintendo 3DS is updated by downloading data from Nintendo's CDN.
CUPs will only deliver updates to core features, such as the Home Menu, Nintendo 3DS Camera etc. CUPs will not deliver updates to Network features, such as System Transfer, Internet Browser, StreetPass Mii Plaza or eShop.
NUPs can deliver updates to core features as well as (updated) Network Features.
As a result of deciding to make a distinction between what content could be updated and how, Nintendo split the system version displayed by System Settings into two parts: CVer (Console Version) and NVer (Network Update Version). Represented as:
<CVer Major>.<CVer Minor>.<CVer Micro>-<NUP Version><NUP Region>
The Console Version represents the version of the collectively installed core features. And the NUP Version represents the version of the collectively installed network features.
So if a 3DS' System Firmware read 2.1.0-2U, it would indicate a console version of 2.1.0 and a NUP version of 2U.
- CUPs can only update core content, so NVer is never updated with CUPs.
- NUPs will not update NVer if network features are not updated. (Best seen with the USA vs JPN/EUR 6.0.0 NUP)
CUPs are implemented by adding a System Update CFA to retail NCSD gamecard images. Nintendo generally creates CUPs after NUPs are released.
When updating the system from 4.5.0-6 to 4.5.0-10, the following titles are updated(in the order of title download+install): Health and Safety Information, Nintendo 3DS Camera, eShop, System Transfer, Internet Browser, 0004009B00014102, 0004009B00014202, 0004009B00014302, NVer, and AGB_FIRM.
 System Versions List
|System version||Home Menu title version||Release date||Changelog||System security flaws fixed*||3DS-mode homebrew affected*||CUP Released||CDN Availability||CDN Post Date|
|1.0.0-0||0||February 26, 2011||Shipped with 3DS on launch||Yes||Available||February 18, 2011|
|1.1.0-1||0||February ?, 2011|| General bug fixes
Added 3D Video title to menu. ("For a Limited Time Only")
|Yes||Available||March 1, 2011|
|2.0.0-2||1029||June 6/7, 2011||eShop added, web browser available, System Transfer added. Full DSiWare data management available. Automatic downloading for system updates added.||No||Available||June 6, 2011|
|2.1.0-3||2049||June 15, 2011||Fixes the Ridge Racer freeze.||Yes||Available||June 15, 2011|
|2.1.0-4||Not updated||July 25, 2011||System stability improvements and other adjustments.||No||Available||July 25, 2011|
|2.2.0||?||November 6, 2011||CUP Only Release. Improved the arrangement of Friend List. Update from some game cards such as Super Mario 3D Land.||Yes||Unavailable||?|
|3.0.0-5||4111||December 7, 2011||Added 3D video recording to the camera title, updated Mii Streetpass Plaza, System Transfer between 3DS systems available, improved eShop, home menu QR code scanning with QR codes containing URLs. Nintendo Zone is now always accessible, 3D video streaming support was added to NZone. This added support for running GBA VC titles via AGB_FIRM as well, support for GBA VC titles was also added to NATIVE_FIRM.||Yes||Available||December 7, 2011|
|3.0.0-6||Not updated||December 21, 2011||Only StreetPass Mii Plaza and the NVer title were updated. From Nintendo's release notes: "System stability improvements and other adjustments".||No||Available||December 21, 2011|
|4.0.0-7||5131||April 24, 2012||Add folders to Home Menu, game patching added, buy more expensive games than 1000 yen in JPN. System titles for CHN, TWN, and KOR became available.||Yes||Yes||Available||April 24, 2012|
|4.1.0-8||Not updated||May 14, 2012||From changelog: "improvements to overall system stability and other minor adjustments". Once updated to 4.1.0-8, the parental-controls PIN is no longer required for future system updates.||Yes||Yes||Available||May 14, 2012|
|4.2.0-9||6146||June 26, 2012||Improved eShop safety for entering credit-card info, and behind the scenes improvements. Stored CC info will be deleted by this updated eShop, and can be re-entered again.||Yes||Available||June 26, 2012|
|4.3.0-10||Not updated||July 24, 2012||Updated eShop, bad word list and NZone hotspot list updated.||Yes||Available||July 24, 2012|
|4.4.0-10||Not updated||September 19, 2012||NZone hotspot list updated and TWL_FIRM updated for blocking flash cards.||Yes||Available||September 19, 2012|
|4.4.0-10C||Not updated||October 17, 2012||China-only, the *only* updated title was System Settings. This title was updated to a version already available in TWN/KOR.||?||Available||October 17, 2012|
|4.5.0-10||Not updated||December 4, 2012||Flash-card block via updated TWL_FIRM and whitelist. NZone hotspot list updated as well.||Yes||Available||December 4, 2012|
|5.0.0-11||7172||March 25, 2013||Many system titles including NATIVE_FIRM were updated, multiple vulnerabilities were fixed as well.||Yes||Yes||No||Available||March 25, 2013|
|5.1.0-11||Not updated||April 4, 2013||NATIVE_FIRM and NS were updated. According to the official change-log: "Resolves an issue that may prevent access to the System Settings or other features."||No||No||Yes||Available||April 4, 2013|
|6.0.0-12 (-11U)||8198||June 17, 2013||Official change-log: "Users can now back up save data for downloadable versions of Nintendo 3DS software and most Virtual Console games". For EUR/JPN, the StreetPass Mii Plaza application and the Nintendo 3DS Camera application were updated. Other titles for all regions were updated as well.||Yes||No||Available||June 17, 2013|
|6.1.0-12 (-11U)||Not updated||June 27, 2013||Official change-log: "Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience."||Yes||Available||June 27, 2013|
|6.1.0-12U||Not updated||July 11, 2013||This USA-only update added the updated network features applications which were first released in JPN/EUR with the 6.0.0-12 NUP update.||No||Available||July 11, 2013|
|6.2.0-12||Not updated||August 6, 2013||This update added support for the StreetPass relay feature, updated TWL_FIRM, and updated the Nintendo Zone hotspots list.||Yes||Available||August 6, 2013|
|6.3.0-12||Not updated||September 13, 2013||See this.||No||No||No||Available||September 13, 2013|
|6.4.0-12||?||November 11, 2013||See this(Only for the KOR and TWN regions).||No||Available||November 11, 2013|
|7.0.0-13||9230||December 9, 2013||See this.||Yes||No||Available||December 9, 2013|
|7.1.0-14||Not updated||December 19, 2013||See this.||No||Yes||Available||December 19, 2013|
|7.1.0-15||Not updated||January 22, 2014||See this.||No||No||No||Available||January 22, 2014|
|7.1.0-16||Not updated||February 26, 2014||See this.||No||No||No||Available||February 26, 2014|
|7.2.0-17||Not updated||May 12, 2014||See this.||No||No||Available||May 12, 2014|
|8.0.0-18||Not updated||July 7, 2014||See this.||No||No||No||Available||July 7, 2014|
|8.1.0-18||Not updated||July 24, 2014||See this.||No||No||No||Available||July 24, 2014|
|8.1.0-19||Not updated||August 7, 2014||See this.||No||No||No||Available||August 7, 2014|
|8.1.0-0 New3DS||Not updated||September 26, 2014||See this.||No||No||Available||September 26, 2014|
|8.1.0-19||Not updated||October 2, 2014||Japan-only "update", see here. The only change was that a new title(New_3DS-only system application) was added, CVer/NVer titles were not even updated. The initial version of this title is a stub.||No||No||No||Available||October 2, 2014|
|9.0.0-20||v11272||October 6, 2014||See this.||No||No||Available||October 6, 2014|
|9.1.0-20J||v14336(JPN-region title)||October 10, 2014||Japan-only, see this.||No||No||No||Available||October 10, 2014|
"System security flaws fixed*": This includes known flaws, and any fixed flaws discovered via code bin-diff. This does not include ARM11-userland ROP entrypoints unless specifically mentioned otherwise on the system-update page.
"System security flaws fixed*" and "3DS-mode homebrew affected" only apply to the changes done with that specific system-update.
 Auto-Boot Function
When the Home Menu is initially loaded by NS, it checks the gamecard ExeFS:/icon for the auto-boot flag. If the auto-boot flag is set, it will load the application on the cartridge and the home menu will not remain running in the background, or at least not in an operational state. Using software cues to return to the home menu, or sleep menu while in this state, causes a shutdown.
Notable features of demo titles:
- Auto-boot demos generally disable the functionality of the home button.
- The New Super Mario Bros 2 demo, retained the functionality of the home button, and had an timer which triggered the demo to quit after a period of inactivity.
Auto-boot cartridges, can bypass some of the functions of the Home Menu. Auto Booted software:
- Doesn't show usage history in the Activity Log
- Bypasses Parental controls
- Bypasses Forced Game Card Updates
- Bypasses Initial 3DS Setup
- The console does not have a friends list presence.
- Is still subject to region lock(see below).
Region lock is still active, so the home menu will refuse to launch demos with incorrect region lock will not load, displaying "An Error has Occurred". However, game card update partition checks are not done, which allows launching demos that have region free encoding, but have an alternate(or even invalid) region update partition.
The following auto-boot paths can be used by Home Menu, checked in the same order listed below(the above gamecard auto-boot is checked before this):
|Key-combo / requirements for this path||Description|
|R, L, and X||This launches System Settings for touchscreen calibration.|
|R, L, and Y||This launches System Settings for circlepad calibration.|
The following is only checked when the low u16 from config block 0x00110000 is value zero(normally this is non-zero). Thus, the below is only handled when a system setup is required.
|Key-combo / requirements for this path||Description|
|R, X, Y, A, and B, a 3DS gamecard must be inserted as well.||This launches the gamecard application. Note that pressing the HOME button in the gamecard application launched this way will only result in the system shutting down.|
|This is used when the above path isn't used.||This launches System Settings for the system setup.|
 Region Lockout
One of the Home Menu's functions, is to regulate region lockout. The region lockout data for any given title is held in the ICN data. There are 6 regions of which have their own region lockout, Japan, USA, Europe(including Nintendo Australia), China, Taiwan and Korea. There is also a value which makes a title exempt from region lockout, and consequently accessible from any region of 3DS.
The region-field stored in the ICN-data is only checked when Home Menu itself launches a title, not when other titles use NS to have Home Menu launch titles. This isn't actually useful for gamecard region-free however, due to the gamecard system-updates, see below.
Also note that while some gamecard games are mostly region-free(main CXI is identical for all regions of the gamecard), those gamecards can't actually be launched with all 3DS regions due to the gamecard system-update, see below. Note that the main CXI being identical for all regions of a gamecard also means the savedata keyY is identical for all regions of that gamecard too(except for old system-version <v2.2 games, in some cases, due to different cardIDs).
 Effects of Region Lockout
Every 3DS title regardless of location (NAND/SD Card/Game Card) is subject to region lockout scrutiny by the Home Menu. And the home menu treats 'out-of-region' titles by simply refusing to show them on the home menu. No messages are shown on the home menu to notify the user, the title is simply ignored. However out-of-region SD Card titles, will appear and quickly disappear, while all the SD Titles are being processed. In cases where access to the home menu GUI is not needed to launch the title (like in the case of kiosk demos), the home menu states an error has occurred, and launching of the title is stopped.
 Game Card Updates
Either intentionally a region lock mechanism or not, the function which checks the game card update partition returns an error when it is detected the update is for a region other than the 3DS's region (Most likely triggered by the absence of the correct CVer title). And errors returned from checking the update partition, will result in the home menu displaying "This Game Card cannnot be used", when the user attempts to launch the title.
Home-menu uses two domains with HTTPS for SpotPass. SpotPass stores this content in Home-menu's NAND shared extdata.
- The system notifications are downloaded from: https://a248.e.akamai.net/f/248/103046/10m/npdl.c.app.nintendowifi.net/p01/nsa/<regionID>/<filename>/<langcode>/<filename> Where langcode is the two-character language codes from config, and regionID is from the below table. <filename> is bashoX/sysmsgX where X is 0-3.
- https://pls.c.shop.nintendowifi.net/pl/upload This URL is used for uploading data from the home menu NAND shared extdata, it's unknown what this is used for. This data is uploaded every 24 hours.
- https://npul.c.app.nintendowifi.net/p01/recv/<regionID>/<filename> This is used for uploading unknown data from extdata. <filename> can be "phu", "tiu", "splu", or "sendmgn".
|EUR / Others||UrXSeurnxhPrq7AS|
The SpotPass content payload for notifications begin with a header, followed by an icon and the UTF-16 text, and various metadata.
 Automatic System Update Download
 Home Menu Error Messages
|"An error has occured. Please save your data ... then restart the system"||This dialog is displayed when a system process(including Home Menu) crashes/terminates. This dialog is also displayed for system errors as well.|
 SD ExtData
The SD ExtData File System for Home Menu is as follows:
root ├── icon ├── boss └── user ├── SaveData.dat ├── Cache.dat └── CacheD.dat
|icon||Stubbed. Always image 00000002.||0x4 Bytes||n/a|
|SaveData.dat||Always image 00000003.||0x2cb0 Bytes||1.0.0-0||Download|
|Cache.dat||Indexes and records details for the cached icon data. Always image 00000004.||0x1688 Bytes||1.0.0-0||Download|
|CacheD.dat||Cached icon data for Home Menu. Always image 00000005.||0x4cfe00 Bytes||1.0.0-0||Download|
 Cache.dat & CacheD.dat
These two files work in tandem to allow the home menu to cache icon data for applications which are presented on the Home Menu. The size of both files suggests a maximum cache size of 360 icons. Cache.dat stores details about the cache icon data, and CacheD.dat stores the icon data. The icon cache stores icon data for *all* applications shown on the Home Menu, this includes DSi NAND Titles, and DS(i) cartridges. The format of cached DS(i) icon data is not understood, but they are the same size as 3DS icon data (0x36c0).
In Cache.dat the first 8 bytes are reserved, then follows each icon slots's entry in the format:
|0x0||8||Title ID in Little Endian|
All unused entries have the Title IDs filled with "0xff".
In CacheD.dat, the icon data is concatenated together, with the first icon at offset 0x0.