Did you expect anyone to jailbreak iOS4 within 1 day from release? Now when iPhone OS 4.0 is iOS 4 and GM Candidate is available for download, jailbreak community have put their attention to jailbreak iOS 4. We may see Sn0wbreeze 1.6 from iH8sn0w soon that will enable you to jailbreak iOS 4. We are sure there’d be quite many things lined up by iPhone hackers. In the mean time you can use Redsn0w 0.9.5 Beta to jailbreak iOS 4, as it was previously announced for iPhone OS 4.0.

You can follow the step by step guide we earlier posted to jailbreak iOS 4 with redsn0w 0.9.5 Beta. If you’re on an unofficial carrier with unlocked iPhone, you should stay away from iOS 4 for now as there is no tool available to unlock iOS 4 up till now. However there are rumors that iOS 4 unlock is in making and would be released soon. So we recommend you stay on iPhone 3.1.3 for now and wait for the updated ultrasn0w or blacksn0w for iOS 4.

Update 1: iPhone Dev Team have confirmed that Redsn0w 0.9.5 can jailbreak iOS 4, here is the official word:

For those who can legitimately activate to the iPhone3G 4.0GM seed, the “point to previous IPSW” redsn0w trick works and will jailbreak your 4.0GM. The “trick” is to point redsn0w at the 4.0beta4 IPSW instead of 4.0GM (do this after you’ve updated to 4.0GM and activated through the new iTunes 9.2 on your Mac). Since the carrier unlocks aren’t yet supported at 4.0, don’t do this if you use yellowsn0w/ultrasn0w/blacksn0w. Many JB apps are still pretty buggy in 4.0, so again this is mostly useful only for developers of those JB apps.

Note: If you’re experiencing MobileSafari crashes, double check that you’re running the version at the bottom of this page.

For those without legit iPhone3G 4.0GM seed access, please wait until the full public 4.0 release for updates to the jailbreak tools.

Update 2: Thanks to msftguy, PwnageTool can jailbreak iOS 4 on iPhone 3GS.

Update 3: Redsn0w 0.9.5 has been updated to jailbreak iOS 4, download redsn0w 0.9.5 Beta 5.