Cthulu 3DS

From GameBrew

Last Updated2019/11/28

Cthulhu is a 3DS homebrew application for managing play time history, step history and cached icon data.

The goal of this app is to provide an open-source alternative to some of the 3DS Development Unit Software, alongside with extra features.


  • Clear play time history.
  • Clear step history.
  • Clear and/or edit software library.
  • Clear, update and/or restore shared icon cache.
  • Clear, update and/or restore Home Menu icon cache.
  • Reset demo play count.
  • Reset folder count.
  • Unwrap and/or repack all Home Menu software at once.
  • Remove software update notifications (with exceptions).
  • Clear game notes.
  • Replace and/or restore eShop BGM.
  • Change accepted EULA version for allowing out-of-region online play.
  • Toggle Home Menu/Test Menu on startup (requires UNITINFO patch and Test Menu installed).
  • Set play coin count to 300.


Available in a 3DSX (latest) and CIA formats.

  • 3DSX - Copy .3dsx to sdmc:/3ds/Cthulhu then run with Homebrew Launcher.
  • CIA - Install .cia with the CIA manager of your choice.

Notes from developer:

It is recommendeded to use the 3DSX version with Luma3DS 9.0. Work just as fine as the CIA (available in v1.3.4 and prior releases) and without cluttering your activity log.

Also always make a backup of your activity log savefile before using software library features.

User guide

Play time/step history

Clear play time history Clears your play time history (can be seen under Daily Records> Activity Log).
Clear step history Clears your step history (can be seen under Daily Records> Activity Log).
Clear software library Clears your software library (can be seen under Software Library> Activity Log).
Edit software library Allows editing of individual entries on your software library.

Cache icon data

Clear shared icon cache Clear all shared cached icon data, used by Activity Log, Friends List and Notifications (this will also clear your Activity Log title list).
Update shared icon cache Iterates through all entries and replaces outdated ones.
Restore shared icon cache Restores the previous shared icon cache in case something goes wrong while updating it.
Clear HOME Menu icon cache Clears the icon cache used by Home Menu, then reboots the console so Home Menu can create it again.
Update HOME Menu icon cache Iterates through all entries and replaces outdated ones.
Restore HOME Menu icon cache Restores the previous Home Menu icon cache in case something goes wrong while updating it.


Reset demo play count Resets the play count of all installed demo software.
Reset folder count Resets Home Menu's folder count so that the next folder created is 1 (only works if you run Cthulhu from Test Menu).
Unwrap all HOME Menu software Unpacks all gift-wrapped software on Home Menu.
Repack all HOME Menu software Gift-wraps all software on Home Menu. Mainly intended for testing the above feature.
Remove software update nag Installed titles will no longer ask for an update when launched (until Home Menu downloads version data again).
Cannot be used to bypass the hardcoded version check on Ironfall: Invasion.
Clear game notes Clear all of your game notes.


Replace eShop BGM Replaces the current eShop music with a custom one.
Restore eShop BGM Restores the default current eShop music.
Change accepted EULA version Useful for allowing out-of-region online play (when set to FF.FF).
Toggle HOME/Test Menu Changes which menu the 3DS will boot on startup (requires both UNITINFO patch and having Test Menu installed for it to work).
Set play coin count to 300 The system's cap.


3DS Homebrew: Cthulhu (German) (NintendoBrew)

Known issues

Because Home Menu doesn't allow accessing its icon cache while it's running, Cthulhu runs on extended memory mode.

Clearing or updating Home Menu icon cache may uninstall sdiconhax (a.k.a menuhax 3.x).


v1.3.5 2019/11/28 (3DSX only)

  • Small release that adds an option to set play coins to 300, the system's cap.
  • This codebase is old and will likely not be updated again.

v1.3.4 2018/03/16

  • This releases fixes a crash when trying to backup anything without having a /3ds/data/cthulhu folder on the SD card. Current working directory is sdmc:/3ds/Cthulhu.

v1.3.3 2018/01/6

  • Loading and saving of software library is now instantaneous.
  • Fix crashes upon editing software library.
  • Update to latest ctrulib.

v1.3.2 2017/05/28

  • Cthulhu now checks if test menu is installed before attempting to switch to it.

v1.3.1 2017/05/25

  • Support for Korean/Taiwan/Chinese HOME Menu.
  • Switch between HOME Menu and Test Menu.
  • Fix software library not being cleared (activity log will still reload data from PTM though, rendering this useless).

v1.3.0 2017/03/26

  • This release fixes Cthulhu not working on the New 3DS and adds "accepted EULA version" setting for out-of-region online play. (Credits go to @SciresM for his EULASetter app.)

v1.2.0 2017/02/17

  • Finally, software library editing is here. Although some features like moving and sorting entries are still missing.
    • Warning: always make a backup of your activity log safefile before using this.
    • Go to "Activity Log management" then "Edit software library".
    • Once the list loads, you can either press A to edit a entry, X to remove it, or Y to list/delist it.
    • Pressing A will take you to another menu, where you can view detailed info about a title.
    • Select a field, press A to edit it and up/down to modify values.

v1.0 2016/08/28

  • First stable release. Check the readme for info.

External links