Windows Stop Code List: What Each Blue Screen Actually Means

Quick answer: A Windows stop code is the name of the safety check that failed when your PC crashed, such as CRITICAL_PROCESS_DIED or DRIVER_IRQL_NOT_LESS_OR_EQUAL. Write it down, because it sorts the problem into one of three buckets: a driver (update or roll it back), hardware (test RAM, drive and temperatures), or boot and storage (startup repair, storage settings, or undoing an update). The table below gives the first fix for the codes people actually see. If the code changes from crash to crash, suspect hardware first.

The blue screen has a reputation it does not entirely deserve. It looks like a catastrophe. It is actually Windows doing its job: noticing that something in the deepest layer of the system has gone wrong and stopping everything before a bad driver or a failing memory chip can quietly corrupt your files.

The stop code is the one piece of the screen that matters. It is not a random error number. Each one names the specific check that failed, and Microsoft documents several hundred of them. You only need to recognise about fifteen.

On recent Windows 11 builds the screen is black instead of blue and shows less text, but the stop code is still printed on it, and the QR code still leads to windows.com/stopcode, which is Microsoft's generic troubleshooting page. That page will not tell you much about your specific code. This one will.

First, capture the code properly

The screen often disappears before you can read it. Two ways to get the code back after the reboot:

1. Open Event Viewer, go to Windows Logs, then System, and filter for source BugCheck (Event ID 1001). The entry reads The bugcheck was: 0x000000xx, followed by four parameters.
2. Open the minidump files in C:\Windows\Minidump with NirSoft's free BlueScreenView, which shows the code name and the drivers involved in each crash.

Reliability Monitor (type perfmon /rel into the Start menu) is the third option and the most underrated. It shows every crash on a timeline next to every driver install and Windows update, which often answers the question "what changed?" in about ten seconds.

The three buckets

Before the list, the logic behind it.

Driver codes fire when a driver touches memory it should not, at a moment it should not. The fix is almost always a driver update, rollback or removal.

Hardware codes fire when the processor, memory, storage or power delivery reports an error, or when data that should be correct turns out not to be. The fix starts with testing, not reinstalling.

Boot and storage codes fire when Windows cannot reach or trust its own system drive during startup. The fix usually happens in the recovery environment.

The most useful pattern is the simplest one: the same code with the same driver every time is software. Different codes every time is usually hardware.

The Windows stop code list

Driver codes

DRIVER_IRQL_NOT_LESS_OR_EQUAL (0xD1) and IRQL_NOT_LESS_OR_EQUAL (0xA). A driver accessed memory at a priority level where that is forbidden. The D1 version usually names the driver; network, Wi-Fi and antivirus drivers are common. First fix: update or roll back the named driver.

SYSTEM_SERVICE_EXCEPTION (0x3B). Code crashed while Windows was handling a request from a program. Graphics, VPN, webcam and security drivers lead the list. We wrote a full SYSTEM_SERVICE_EXCEPTION guide because it is one of the most searched codes.

SYSTEM_THREAD_EXCEPTION_NOT_HANDLED (0x7E) and KMODE_EXCEPTION_NOT_HANDLED (0x1E). A kernel thread threw an error nobody caught. Same playbook: find the named driver, update or roll it back.

VIDEO_TDR_FAILURE (0x116). The graphics driver stopped responding and Windows could not reset it. Clean install the graphics driver. If it continues under load, check GPU temperatures and the power supply.

DPC_WATCHDOG_VIOLATION (0x133). A driver took too long to finish its work. Historically associated with SSD firmware and storage controller drivers. Update SSD firmware with the drive maker's tool and update chipset drivers.

DRIVER_POWER_STATE_FAILURE (0x9F). A driver failed to handle sleep, wake or shutdown. Common on laptops after waking from sleep. Update Wi-Fi, graphics and chipset drivers, and check the laptop maker's support site for a BIOS update.

Hardware codes

WHEA_UNCORRECTABLE_ERROR (0x124). The processor itself reported a hardware error. Causes include overclocks (CPU or memory), overheating, insufficient power and, occasionally, a failing CPU. First fix: remove every overclock including XMP or EXPO memory profiles, then check temperatures.

MEMORY_MANAGEMENT (0x1A). Windows found its memory bookkeeping corrupted. Usually RAM or a memory overclock. See our MEMORY_MANAGEMENT fix guide for the full RAM testing process.

PAGE_FAULT_IN_NONPAGED_AREA (0x50). Something requested memory that should always be present and found nothing there. Bad RAM, a bad driver or antivirus software are the usual causes. Run Windows Memory Diagnostic, then check the driver named in the dump.

CLOCK_WATCHDOG_TIMEOUT (0x101). One processor core stopped responding to the others. Often an unstable CPU overclock, undervolt or outdated BIOS. Reset the BIOS to defaults and update it.

KERNEL_DATA_INPAGE_ERROR (0x7A) and NTFS_FILE_SYSTEM (0x24). Windows could not read data it needed from the disk. These are early warnings of a failing drive or a loose cable. Back up immediately, then check the drive's SMART health with CrystalDiskInfo and run chkdsk C: /scan.

Boot and storage codes

INACCESSIBLE_BOOT_DEVICE (0x7B). Windows lost access to its own system drive during startup. The most common triggers are a BIOS storage setting that changed (AHCI, RAID or Intel VMD mode), a failed Windows update, or a failing drive. If you changed BIOS settings recently, change them back. Otherwise use Startup Repair from the recovery environment, then try Uninstall Updates there.

CRITICAL_PROCESS_DIED (0xEF). A process Windows cannot run without stopped unexpectedly. Corrupted system files and failing drives are the common causes. Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth, from Safe Mode if needed.

0xc000021a. A core user-mode process such as winlogon or csrss failed, usually after an interrupted update or a damaged system file. Startup Repair or System Restore from the recovery environment fixes most cases.

UNEXPECTED_STORE_EXCEPTION (0x154). Despite the name, nothing to do with the Microsoft Store. It concerns memory compression and paging, and often points at the drive or its driver. Check drive health and update storage drivers and SSD firmware.

Security codes

KERNEL_SECURITY_CHECK_FAILURE (0x139). Windows detected that a kernel data structure was tampered with or corrupted. Usually a driver bug, sometimes memory. Rarely, malware. Update drivers first.

CRITICAL_STRUCTURE_CORRUPTION (0x109). Kernel code or critical data was modified. Causes include faulty drivers, bad memory and, in rare cases, rootkits. Test memory, update drivers, and run a Microsoft Defender Offline scan.

Getting into recovery when Windows will not start

Boot codes often mean Windows never reaches the desktop. Power the PC off as soon as the manufacturer logo appears, three times in a row. On the next start Windows opens the recovery environment. From Troubleshoot, Advanced options you get Startup Repair, Uninstall Updates, System Restore, Startup Settings (for Safe Mode) and a Command Prompt.

If even that fails, a Windows 11 installation USB made with Microsoft's Media Creation Tool on another PC gets you into the same recovery tools. A spare 32GB or 64GB USB flash drive is worth keeping in a drawer for exactly this purpose.

When the stop code points at malware

Malware is a rare cause of blue screens, and the codes most often associated with it are the security ones: KERNEL_SECURITY_CHECK_FAILURE and CRITICAL_STRUCTURE_CORRUPTION, plus any crash naming a driver you cannot identify online. Start with the free tools you already have, covered in our free malware scanner guide. If you want a second engine that does not share Defender's detection logic, Iolo Malware Killer runs as an on-demand scan alongside it. It will not fix a driver or hardware fault, so rule those out first.

Watch out for fake blue screens. A browser page that goes full screen, shows a blue screen and a phone number is a tech support scam, not a crash. Real stop codes never include a phone number. Close the browser with Ctrl + Shift + Esc and Task Manager.

Frequently Asked Questions

What is a stop code in Windows?

A stop code (also called a bug check code) is the identifier Windows displays when it halts the system to prevent damage. It names the specific check that failed, such as CRITICAL_PROCESS_DIED or MEMORY_MANAGEMENT, and it is the best starting point for diagnosing a blue screen.

Where do I find my Windows stop code after a crash?

Open Event Viewer, go to Windows Logs, then System, and look for events from the BugCheck source. You can also read the minidump files in C:\Windows\Minidump with BlueScreenView, or see each crash on a timeline in Reliability Monitor (perfmon /rel).

Is the windows.com/stopcode page useful?

Only in a general way. The QR code on the crash screen sends everyone to the same Microsoft troubleshooting page regardless of the code. Searching your specific stop code name gets you much closer to a fix.

Can a blue screen fix itself?

A single crash after an update sometimes never returns, because a later update fixes the driver. Repeated crashes with the same stop code will not go away on their own and usually get more frequent, especially when hardware is involved.

Does the same stop code always mean the same problem?

No. A stop code tells you which check failed, not why. MEMORY_MANAGEMENT can be bad RAM or a bad driver. The driver named in the crash dump and whether the code repeats are what separate one cause from another.