About This Firmware
iOS 4.2.1
(build 8C148a) is an official Apple IPSW
for the iPhone 3GS.
The download is 401.32 MB and is served directly from Apple's CDN.
This firmware is no longer signed by Apple. Standard downgrades are not possible, but the file remains available for reference and advanced use.
Verify the download using the checksums below.
Filename
iPhone2,1_4.2.1_8C148a_Restore.ipsw
Checksums
SHA-256
09f3617fcf3e419e12c4a3c62f1fe0ab3909d0573a00937584124f869a7df15d
SHA-1
2787bb9fbf18594279d05682e6fd16d2b9612a2a
MD5
d688d2d48c8b054367adef8e7ab4f5ea
Direct URL
https://secure-appldnld.apple.com/iPhone4/061-9895.20101122.Cdew2/iPhone2,1_4.2.1_8C148a_Restore.ipsw
Other Devices
iPhone 18 Pro
iPhone19,2
iPhone 11 Pro
iPhone12,3
iPhone 5s (Global)
iPhone6,2
iPhone X (Global)
iPhone10,3
iPhone 15 Plus
iPhone15,5
iPhone 13 mini
iPhone14,4
How to Restore with This IPSW
iTunes / Finder
macOS & Windows- Download the .ipsw file to your computer.
- Connect your iPhone 3GS via USB.
- Open iTunes (Windows / macOS Mojave and earlier) or Finder (macOS Catalina+) and select your device.
- Update (keep data): hold Option (Mac) or Shift (Windows) and click Update, then pick the .ipsw file.
- Restore (erase & install): hold Option / Shift and click Restore iPhone…, then pick the .ipsw file.
- Wait for the process to finish - do not disconnect.
Restoring will erase all data on the device. Back up first.
3uTools
Windows- Download and install 3uTools from 3u.com.
- Connect your iPhone 3GS via USB and trust the computer on the device.
- Go to Flash & JB > Easy Flash.
- Click Import and select the downloaded .ipsw file.
- Choose Flash mode: Update keeps data, Restore wipes the device.
- Click Flash and wait for the progress bar to complete - do not disconnect.
Only flash firmware that matches your exact device model.
DFU Mode
Recovery tipIf your device is stuck in a boot loop or iTunes/Finder does not recognise it, enter DFU mode first, then select the .ipsw file as normal.
iPhone 8 / X and later
- Quickly press & release Volume Up
- Quickly press & release Volume Down
- Hold Side button until screen goes black
- Hold Side + Volume Down for 5 s
- Release Side, hold Volume Down 5 more s
- Black screen = DFU active
iPhone 7 / 7 Plus
- Hold Sleep/Wake + Volume Down for 8 s
- Release Sleep/Wake, keep holding Volume Down for 5 s
- Black screen = DFU active
iPhone 6s and earlier
- Hold Sleep/Wake + Home for 8 s
- Release Sleep/Wake, keep holding Home for 5 s
- Black screen = DFU active