Carrier Bundle

Carrier Bundles provide a way to organize all customizations related to carriers in one place. These include voice mail numbers, MMS and APN settings etc.

For users on carriers other than the Apple's official partners, carrier bundles allow to configure important settings such as APN and enable features like MMS and tethering.

On the device side, carrier bundles are stored in the following directories:
 * /var/mobile/Library/Carrier Bundles/ - bundles downloaded via iTunes.
 * /System/Library/Carrier Bundles/ - bundles provided with the firmware image. Starting with iOS 4.2, carrier bundles are stored in a subfolder of this path.

If two bundles with the same name exist in both paths, the one on user partition takes preference. This allows Apple to update carrier bundles without releasing a whole new OS.

On a computer that has downloaded carrier bundle updates, they are stored in the following directories:
 * ~/Library/iTunes/iPhone Carrier Support/ - this folder will not exist if iTunes hasn't downloaded any carrier updates

Structure
Carrier bundles are ZIP archives with .ipcc extension. They are named after the carrier and the country they are for (for example, ) They contain the mandatory Payload folder that includes the bundle itself and the symlink:

\Payload\ \MyCarrier_au.bundle\ \carrier.plist - carrier settings go here \Default_CARRIER_MyCarrier.png - logo for grey status bar \FSO_CARRIER_MyCarrier.png - logo for black statusbar \Info.plist - bundle description \version.plist - bundle version (not always present) \12345 - symlink to MyCarrier_au.bundle (12345 is MCC+MNC)

Enabling .ipcc support in iTunes
By default, iTunes allows only carrier bundle updates from Apple. However, when the "carrier-testing" preference is enabled, .ipcc files can be loaded from the user's hard drive by clicking either "Check for Updates" or "Restore" button while holding Shift (on Windows) or Option key (on Mac).

To enable this preference, first close iTunes, then run the command below that corresponds with your OS:
 * macOS 10.14 and older:
 * macOS 10.15 and newer:
 * Windows:

iOS 3.1 Changes
As of iOS 3.1b1, APN settings are now being signed to prevent tampering/modification by users. This has been implemented to stop users bypassing the carrier's designated APN for tethering that may require payment for access. This is also a concern for users of carriers that do not officially offer MMS or Tethering services for users at all. This signature-check can be circumvented by patching commcenter.

Only the APN settings are being signed; other settings can still be modified without needing to patch commcenter.

iOS 4.x Changes
One of the new 'features' in iOS 4 is the addition of over-the-air carrier updates. Carriers can now push updated settings over the air without having to tether your device to a computer to poll for updates. All carrier bundle settings are now signed, not just the APN settings. To circumvent this, commcenter must now be patched. The bit-mask for APN settings has also changed quite significantly.

Type Mask
''These flags are deprecated for iOS 4 and above. These will need to be updated for 4.0 onwards.''

Each APN in the carrier.plist has a numeric type-mask. It is bitmask (combination of flags) that designates what the APN should be used for (eg. phone data, tethering, visual voicemail, MMS, or a combination). This table shows what each-type mask designates an APN for.

For example, 55 = 1+2+4+48 means "Tethering, MMS, VVM, Data"