iPhone 3GS Stuck in Endless Boot Loop After Accidental Software Update

This explains how to put a device into Recovery Mode. If you can't update or restore your iPhone or iPod touch - Apple Support

However, I doubt that you would be able to do it with an iPhone 3GS, which would have been considered obsolete by Apple. I don't know if I can even determine what version of iTunes it would need and that you would be able to find a download for it. And the two utilities that you mention are for jailbreaking a device and if you try that, you will brick it for sure.

Also, I don't know if a cellular carrier would be able to support that device for phone calls, etc. The chip in that phone does not support any of the current cellular frequencies.

“I did this and i tried to flash it with iTunes but it fails at like 32% and when the bar (on the phone) is at like 5-10%. now instead of being stuck in a boot loop, it shows this”

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It’s time for a New iPhone:

Your iPhone’s just old, and may just not work for such an older iOS off if Apple’s server. As mentioned: use this iPhone as a portable music player.

The iPhone 3GS can't run modern apps. It has a 32-bit processor, and cannot update past iOS 6.

Its cellular radios are 2G/3G ones. In many parts of the world, carriers have permanently shut down 2G and 3G networks, rendering this iPhone useless as a phone.

The camera is a 3 megapixel one, with the tiny sensor and fixed-focal-length lens characteristic of nearly every smartphone camera. I wouldn't expect much with regards to picture quality.

You could, perhaps, use this iPhone as a portable music player.

"iPhone 3GS Stuck in Endless Boot Loop After Accidental Software Update: [...]What I’m looking for is a clear, step‑by‑step explanation of how to get my 3GS out of this boot loop."

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Being Stuck in a Boot Loop:

Update your version of iTunes to the latest version (it would have bug and vulnerability fixes). Your iPhone apparently is stuck in a boot loop. And this typically happens when you unsuccessfully download somethings or an install stalls.  So, refer to my User Tip: How to Fix an iPhone in a Boot Loop - User Tip

If you have an older Mac lying around that runs an old version of iTunes you could try that, too. But it may be bricked.

hey! I'm in the process of trying to access an old 3gs and just got stuck in a bootloop - manually forcing DFU got it out but I've yet to activate the phone to actually use it.

this exact instruction got it out the loop though (make sure the phone has enough battery to do it & also my home button is kinda sticky so i press harder than i think i should)

Put your iPhone into DFU mode:

Open iTunes and connect your iPhone. While it's stuck on the apple logo, hold down the power and home buttons until the screen goes black. As soon as this happens, hold down the power button for three seconds, then the power and home buttons for ten seconds, then release the power button and continue holding down the home button for 15-20 seconds. (all this while connected to your computer). iTunes should tell you that your iPhone is in recovery mode, and you need to restore it. Click the restore button and you should be good.

( it was found here: https://apple.stackexchange.com/questions/115457/resetting-jailbroken-device-in-settings-caused-boot-loop)

for reference my itunes is version 1.0.6.10 on catalina 10.15.7

this is a recent article which breaks down how to activate a 3gs without a sim but i haven't quite succeeded yet - if i do i'll report back!

https://www.seandeaton.com/activating-an-iphone-3g-in-2025/

good luck

Good luck.