How to Fix SW REV CHECK FAIL on Samsung (2026 Guide)

You loaded your firmware into Odin, pressed Start, and within seconds it stopped with a red failure mentioning a software revision check. Nothing was installed, and the same firmware fails every time you retry.

This is not a broken download, a bad cable, or the wrong version of Odin. Your device refused the firmware on purpose. This guide explains why, and what actually resolves it.

Before you try anything

✔️ Confirm your exact device model — including the trailing letters, which distinguish hardware variants.
✔️ Check your installed build — the Build number in Settings tells you what you are moving from.
✔️ Verify the firmware region (CSC) — it decides which package applies to your device.
✔️ Back up your data if the device still boots — before choosing any file.

If you cannot confirm the first three, stop and establish them first. Guessing is what turns a refused flash into a real problem.

Quick answer
Why the device refused it
When this error appears
Is it really SW REV CHECK FAIL?
How to fix it, step by step
Can you fix it without losing your data?
How to avoid it: check before you download
What will not work — and what to avoid
Frequently asked questions

Quick answer

SW REV CHECK FAIL means the firmware you tried to flash contains a bootloader older than the minimum your device will accept. Samsung enforces this in hardware, and the restriction cannot be lifted. The fix is to flash firmware whose build is equal to or newer than the one currently installed — for your exact model and region. Retrying, re-downloading, or switching to a different Odin build will not change the outcome, because the refusal comes from the device rather than from the tool.

Why the device refused it

Samsung devices carry hardware fuses that record the minimum acceptable bootloader version. Samsung’s own security documentation describes them as encoding “the minimum acceptable version of Samsung-approved bootloaders”, and states that once a newer approved bootloader is installed, the device “fuses the version of that bootloader to hardware, preventing old software from being loaded”.

The purpose is security: older firmware can contain vulnerabilities that were later patched, and rollback prevention stops a device being pushed back onto them.

Crucially, Samsung also states that “once the fuse version number is set, it is impossible to revert back to legacy software versions”. That is why this particular failure has no workaround — the limit is physical, not a setting. Source: Samsung Knox — Hardware-Backed Security.

For the full background on how bootloader versions work, see the Samsung bootloader version guide.

When this error appears

You will typically meet it in one of these situations:

Deliberately downgrading. You disliked an update and tried to return to the previous firmware.
Reinstalling an old file you had saved. The firmware worked on this device once, but the device has since updated past it.
Downloading by model name rather than build. The package is genuinely for your model, but it is an older release than the one installed.
Flashing a second-hand device. You do not know what the previous owner installed, and you picked an older build.
Restoring after a problem. You reached for a build you knew was stable, without checking whether it predates the installed one.

The common thread is direction: every one of these attempts to move backwards.

Is it really SW REV CHECK FAIL? Telling Odin’s failures apart

Odin failures are easy to confuse, and the wrong diagnosis leads to wasted effort. Identify which category you are looking at before you act. Odin’s exact wording differs between builds, so treat the messages below as categories rather than literal strings to match character for character.

Category	Typical wording (varies)	What it points to	First thing to check
Software revision	References `SW REV CHECK FAIL`	The firmware is older than the device now accepts	The build of the firmware against the build installed
Authentication	References `FAIL! Auth`	Firmware that does not match the exact model, or a signature the device rejects	Your full model code against the firmware you downloaded
Hash / verification	References `SHA256` or a hash mismatch	An incomplete or corrupted download	Re-download the file, and compare a checksum where one is published
Write / connection	References `Complete(Write) operation failed`	The write stopped part-way through	Cable and USB port first; other causes exist, so do not stop there if it repeats
Device not detected	Stuck at `SetupConnection`, or an empty `ID:COM`	The flash never began	That the phone is genuinely in Download mode, then drivers, cable and port

The distinction that matters most

A software-revision failure is not a fault. It is the device refusing by design, because of the rollback prevention described in the section above and documented by Samsung Knox.

If that is genuinely your category, retrying, re-downloading, or switching Odin build will not change the outcome. Only firmware at or above the accepted level can proceed.

An important qualification. The other categories are not all simple faults you can clear. A hash failure or a connection failure usually can be fixed. But an authentication failure is frequently also a refusal by design — a carrier-locked or region-restricted device, or a signature the device will not accept — and no cable, driver or Odin build resolves that either. Do not assume every non-revision failure is a hardware problem waiting to be fixed.

How to fix it, step by step

Read your installed build number. On a device that still boots: Settings → About phone → Software information (wording varies by One UI version). Note it exactly, along with your model number and region code.
Identify a build that is equal to or newer. Compare the build identifier of any candidate firmware against the one installed. If it is older, it will be refused again.
Confirm the model matches exactly. The trailing letters of a model number distinguish hardware variants, and those variants do not share firmware.
Back up before flashing, whichever region file you plan to use.
Flash the newer package following the normal procedure in the Odin guide.

If the device does not boot and you cannot read the build number, choose the newest firmware published for that exact model and region. Going newer is not blocked by this check; going older is what gets refused. A newer package can still fail for unrelated reasons, such as a wrong model variant.

Can you fix it without losing your data?

The error itself and the fix carry different risks. It helps to separate them.

The refused flash

A version rejection is raised at the verification stage, before the package is applied, so in the normal case nothing is installed and the device is left as it was. If your phone still boots and behaves as before, your data has most likely not been touched.

That is an observation, not a guarantee. A flash can stop at different points, and this guide cannot verify the state of your specific device. Treat a booting phone as good news, not as proof.

The data risk comes from the fix

The fix is to flash a build equal to or newer than the one installed. Whether that erases anything depends on which region file you load:

HOME_CSC — intended to keep existing data when the region already on the device matches the one you are flashing. This is conditional. If the regions differ, expect a reset.
CSC — expect internal storage to be wiped.

For what these files are and how region codes work, see Samsung CSC codes explained.

Back up before you try anything

If the device still boots, back up now — through the device’s own backup tools and a copy of anything irreplaceable to a computer. Do this before choosing a file. A backup taken after a reset is worth nothing.

What is not achievable

There is no legitimate way to install firmware below the accepted level. So “keep my data and go back to the older version” is not a goal this error allows. You can move forward, or stay where you are. Avoid tools claiming to bypass the restriction; the claims are not credible and such tools are a known malware vector.

How to avoid it: check before you download

The version-mismatch cause is preventable, and the check costs a minute.

Read what is installed now

Open Settings → About phone → Software information. Wording and nesting vary between One UI versions, so look for the equivalent screen if labels differ.
Write down the Build number exactly as shown.
Write down the model number (for example SM-A155F) and your region or CSC code.

Compare before you commit

Compare the build identifier of the firmware you are considering against the one installed, and do not select something older.

In a Samsung firmware package the BL file and the AP file carry the same build identifier, so your Build number is a practical shortcut for this comparison. If you want to confirm it for your specific download rather than rely on the shortcut, read the BL_ file name inside the extracted package directly — the identifier follows the model code.

See how to check your Samsung firmware version and the bootloader version guide for more detail.

Going forward is not restricted

Installing a newer build is the normal, supported path, and rollback prevention does not stand in its way. Matching your current build is fine too. It is specifically going backwards that this check refuses.

Note that a newer package can still fail for unrelated reasons — a wrong model variant or a carrier-restricted device, for example — so a successful comparison rules out this one cause rather than every possible failure.

If the device will not boot

When you cannot reach Settings, the build number cannot be read on screen. In that case choosing the newest firmware published for your exact model and region avoids adding a version conflict on top of the existing problem.

Be aware of the trade-off: installing a newer bootloader moves the accepted level forward, which closes off older builds permanently. It will also not fix a device whose fault lies elsewhere.

What will not work — and what to avoid

Because this failure is enforced in hardware, a number of common suggestions are simply wasted effort:

Retrying the same file. The result will be identical every time.
Re-downloading the firmware. The file is not corrupt; a hash failure looks different.
Trying another Odin build. The check is performed by the device, not by Odin.
Changing cable, port or PC. Those fix connection failures, which this is not.
Loading only some of the files. Omitting the BL file does not remove the restriction, and partial flashes carry their own risks.

A warning about “fix” tools. You will find software and forum posts claiming to bypass rollback prevention or reset the fuses. Samsung documents these fuses as hardware state that cannot be reverted. Treat such claims sceptically, and be aware that tools of this kind are a common vector for malware. This guide does not cover circumventing device security.

Frequently asked questions

What does SW REV CHECK FAIL mean?

The firmware you tried to flash has a bootloader older than the minimum your device accepts. The device refused it before writing anything.

Did the failed flash damage my phone?

A refused flash does not write anything, so the device is in the state it was before the attempt. If it booted normally before, it should still boot normally.

Can I reset the fuses or force the older firmware?

No. Samsung’s documentation states the fuse version cannot be reverted once set. There is no legitimate procedure that installs firmware below that minimum.

Will flashing a newer build also fail?

No. Rollback prevention only restricts going backwards. Installing an equal or newer build for your exact model and region is the normal, supported path.

Why did this firmware work on this phone before?

Because the device has updated since. When it installed a newer approved bootloader, the accepted minimum moved forward with it.

Is this the same as a FAIL! Auth error?

No. An authentication failure usually points at firmware that does not match your exact model. A software revision failure means the firmware matches but is too old.

Does this trip Knox or void my warranty?

A refused flash writes nothing. Samsung documents the Knox warranty bit as being set when an unsigned kernel is loaded or a critical security feature is disabled — not when a flash is declined.

Research note

This article combines official Samsung documentation with analysis of firmware metadata indexed by ZipFirmware. Where a statement is based on measured data, the article identifies it as measured; where something is not publicly documented, we say so rather than presenting a guess as fact.

Final thoughts

SW REV CHECK FAIL is one of the few Odin failures that is not a fault at all. The device is working exactly as designed, and the only thing that resolves it is choosing firmware that moves forward rather than back.

Once you are comfortable reading a build number and comparing it before downloading, this error stops happening entirely.

How to Fix SW REV CHECK FAIL on Samsung (2026)