How to Fix Odin Errors: FAIL, SetupConnection and More

Originally written by The Droid Guru Staff, updated by Dibyajyoti Kabi. First published February 15, 2018. Updated October 24, 2026.

Most Odin errors come down to four things: a bad USB connection, an old Odin version, firmware for the wrong model, or a bootloader that’s newer than the firmware you’re flashing. Find the exact message in the Odin log below and you’ll know which one it is.

This guide started in 2018 as a fix for one error, Odin failing on .lz4 firmware files after the Galaxy S8 Oreo update. That one is covered further down, but I expanded the guide to cover every Odin error people still hit today.

Key points

Stuck at SetupConnection or no COM port means a driver, cable or USB port problem.
FAIL (Auth) means Odin refused the file, usually because it’s for a different model or it isn’t official Samsung firmware.
SW REV CHECK FAIL means you’re trying to downgrade to an older bootloader. Odin can’t do that.
Complete(Write) operation failed is usually the cable, the port or an old Odin version.
Errors about .lz4 files or “Unsupported dev_type” mean your Odin is too old. Use Odin3 v3.14.4.

Before you try anything else

Run through this list first. It fixes more than half of the Odin errors I see in comments, and it only takes a few minutes.

Use Odin3 v3.14.4, or the patched 3.13.1 if 3.14.4 fails.
Right-click Odin and choose Run as administrator.
Reinstall the Samsung USB driver and restart the PC.
Close Samsung Smart Switch and any other phone software. It can grab the phone before Odin does.
Use the original Samsung cable, or another cable you know carries data.
Plug into a USB port on the back of a desktop PC, not a hub or a front panel port.
Move the firmware files to a short folder path like C:\Firmware, with no spaces or special characters.

If the error is still there after all of that, find it below.

Why is Odin stuck at SetupConnection?

Odin stuck at SetupConnection means the PC sees the phone but can’t talk to it properly. It’s almost always the USB driver, the cable or the port. Reinstall the Samsung USB driver, switch to the original cable, use a rear USB port and close Smart Switch, then try again.

If that doesn’t help, restart the phone into Download mode again and restart Odin. A different PC is the last thing to try, and it fixes it more often than you’d expect.

Why doesn’t Odin show a COM port?

If the box in the top left of Odin stays empty when the phone is in Download mode, Windows hasn’t installed the Samsung driver for it. Reinstall the Samsung USB driver, unplug and replug the phone, and check Device Manager for “SAMSUNG Mobile USB Modem” under Modems or Ports.

A yellow warning icon in Device Manager means the driver didn’t install correctly. Uninstall it there, then run the Samsung driver installer again.

What does FAIL! (Auth) mean in Odin?

FAIL! (Auth) means the phone’s bootloader refused the file Odin sent. Usually the firmware is for a different model number, or the file isn’t signed by Samsung, like TWRP or a patched boot image on a phone with a locked bootloader. Download firmware for your exact model and try again.

Check the model number on the Download mode screen and compare it with the firmware. SM-S938B and SM-S938U are different phones as far as Odin is concerned, even though they’re both a Galaxy S25 Ultra.

What does SW REV CHECK FAIL mean?

SW REV CHECK FAIL means the firmware has an older bootloader version than the one on your phone. Samsung blocks bootloader downgrades, so Odin stops before it writes anything. You’ll need firmware with the same or a newer bootloader version.

The log usually shows something like “DEVICE: 5, BINARY: 4”. The first number is your phone’s bootloader version and the second is the firmware’s.

You’ll also find the version in the build number. It’s the fifth character from the end, so on S938BXXU5BYJ1 it’s 5. Pick firmware with that number equal or higher.

How do I fix Complete(Write) operation failed?

Complete(Write) operation failed means Odin lost the connection or the phone rejected a partition mid-flash. Swap the cable, use a rear USB port, run Odin as administrator and try the patched Odin3 v3.13.1. If it fails at the same file every time, redownload the firmware.

Don’t panic if the phone now shows “An error has occurred while updating the device software”. Put it back in Download mode and flash again once you’ve fixed the cause. Download mode is still there.

Why does Odin freeze when I load the AP file?

Odin isn’t frozen. The AP file is several gigabytes, and Odin checks its MD5 before it lets you continue. On a slow drive this can take a few minutes. Wait until the AP path appears next to the button, then load the other files.

If it never finishes, the AP file is probably damaged or incomplete. Download the firmware again with Bifrost and extract it again.

What does “Only official released binaries are allowed to be flashed” mean?

This message appears on the phone, not in Odin, when you try to flash something that isn’t official Samsung firmware and the phone doesn’t allow it. Either OEM unlocking is off, or Samsung’s device protection is still active. Flash official firmware for your model and it goes through.

If you’re trying to install TWRP or root, you need to unlock the bootloader first. My guide on Developer options, USB debugging and OEM unlock shows where to find that setting.

Why does Odin say Re-Partition operation failed?

Re-Partition operation failed means Re-Partition got ticked in Odin’s Options tab, but the PIT file doesn’t match your phone, or there isn’t one. Untick Re-Partition, leave only Auto Reboot and F. Reset Time ticked, and flash again.

Never tick Re-Partition unless a guide for your exact model asks for it and gives you the matching PIT file.

Odin can’t read .lz4 files or shows Unsupported dev_type

Both errors mean your Odin is too old for the firmware. Samsung started compressing firmware files with LZ4 in early 2018, starting with the Galaxy S8 Oreo update, and old Odin builds can’t read them. Download Odin3 v3.14.4 and the error goes away.

Back in 2018, before newer Odin versions were available, the workaround was to unpack every .tar file, extract the .lz4 files with a modified 7-Zip and repack them. You don’t need any of that now. Any Odin from 3.13 onward handles .lz4 files on its own.

The same goes for errors like “Invalid ext4 image” on recent firmware. Update Odin first before you try anything else.

FAQ

Is my phone bricked if Odin fails?

Almost never. If the phone still turns on to Download mode, it isn’t bricked. Fix the cause of the error and flash the firmware again. A real hard brick, where the phone shows nothing at all, is rare with official firmware.

Does an Odin error trip Knox?

No. A failed flash of official firmware doesn’t trip Knox. Knox only trips when an unofficial file like TWRP, a custom kernel or a patched boot image actually boots on the phone.

Can I use Odin on a Mac?

No. Odin is Windows only. On a Mac, you’d use Heimdall instead, or update the phone with Samsung Smart Switch, which runs on macOS.

Does Odin still work on One UI 8.5?

Yes, on most Galaxy phones. In March 2026 there were reports that Download mode is locked down on the Galaxy S26 series and the Galaxy Z Fold7 with One UI 8.5, and a later report said it opens after you enable Maintenance mode. Samsung hasn’t confirmed either.

That’s it. Read the last line in the Odin log, match it to the section above, and you’ll be flashing again in a few minutes.

Still stuck? Leave a comment with your Galaxy model number (like SM-S938B), the Odin version you’re using and the exact error from the Odin log, and I’ll help you figure it out.

How to Fix Odin Errors: FAIL, SetupConnection, SW REV CHECK and More