As we all know, after releasing the jailbreak software for iPhone 3GS, Geohot also released his unlock method for iPhone 3GS.

Purplesn0w developed by Geohot is an alternative to ultrasn0w developed by the iPhone Dev Team to unlock iPhone 3GS. Geohot claims that his unlocking software actually improves on some of the common issues faced by using the ultrasn0w developed by the iPhone Dev team.The improvements mentioned by Geohot are as follows:

:: Corrects the Wi-Fi connectivity bar that does not show full signal strength

:: Reduces the rapid battery drain
:: Fixes some miscellaneous unlock related issues
Please note that Dev Team has also released an updated version of UltraSn0w (0.9) which also resolves most of the issues mentioned above.

Some important points before we start:

This guide is only for iPhone 3GS users, if you are an iPhone 3G user, please check out our step-by-step guide to unlock iPhone 3G running iPhone OS 3.0 using UltraSn0w.
To use this guide, you must have a jailbroken iPhone 3GS and the iPhone OS 3.0 installed. Please checkout our guide to jailbreak iPhone 3GS on Windows. Alternatively, you can check our guide to jailbreak iPhone 3GS using Redsn0w for Windows users or this one Mac users.
If you are on a T-mobile network
or any carrier without 3G support then, please disable the 3G service before proceeding.
Tap Settings icon > Go to General > Go to Network > Turn OFF the Enable 3G option.

Here is the step-by-step guide to unlocking your iPhone 3GS using purplesn0w:

Step 1: Launch Cydia on your iPhone

Step 2: Press the Manage tab at the bottom of the Cydia Home Screen.

Step 3: On the Manage section of Cydia, click on the second option named Sources.

Step 4: Now press the Edit button displayed on the top right corner of the screen.

Step 5: Press the Add button displayed on the top left corner of the screen.

Step 6: The screen will display a text box where you have to enter apt.geohot.com as the URL and press the Add Source button.

Step 7: Install com.geohot.purplesn0w

Step 8: As a final step, press the Home button and power OFF and then power ON your iPhone. You can do this by following the sequence:
i. Press the Home button for about 3 seconds
ii. Press the Power button on your iPhone
iii. Move the slider to the right. This will power OFF your iPhone
iv. While keeping the Home button pressed – press the Power button again to power ON your iPhone.

Step 9: You should now be able to insert any SIM card you want in your newly unlocked iPhone 3GS!

If you hit any issues with purplesn0w then you can try UltraSn0w by the Dev Team which also unlocks iPhone 3GS. You can checkout our step-by-step guide to unlock iPhone 3GS running iPhone OS 3.0 using UltraSn0w

Please let us know if you found this guide helpful in or Comments section below.