How to check the baseband version?

If your device is running, you can open Settings, click on General, then About and scroll down to Modem Firmware.

If your device is not booting, it's not possible to find it out, but you can make assumptions. If you did not protect your baseband from getting updated, by using custom firmware to upgrade, or, for the iPhone 4, by not allowing iTunes to contact Apple (by changing the hosts file or by having ever run TinyUmbrella), then a normal restore updates the baseband to the version connected to the firmware. Because you cannot downgrade the firmware, the highest version ever installed counts.

Here's an overview of what firmware installs what baseband. Beta versions are not listed.

iPhone 3G and 3GS

iPhone 4

iPad

For versions inbetween, there was no baseband difference, so take the lower version. For example iPhone 3GS iOS3.1.2 was baseband 5.11.07.
last edit: 2011-01-13

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