0xC000021A

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Windows

0xC000021A

A fatal blue-screen stop error (0xC000021A / STATUS_SYSTEM_PROCESS_TERMINATED) where a critical user-mode system process such as winlogon or csrss terminated unexpectedly.

What it means

A fatal blue-screen stop error (0xC000021A / STATUS_SYSTEM_PROCESS_TERMINATED) where a critical user-mode system process such as winlogon or csrss terminated unexpectedly.

Likely cause

Corrupted system files, a mismatched or interrupted Windows update, or incompatible system software.

How to fix it

Boot into Recovery and run `sfc /scannow` and `DISM /Online /Cleanup-Image /RestoreHealth` (targeting the offline image), use Startup Repair, or roll back the last update. Use System Restore if the problem persists.

Other Windows errors

0x80070005 Access denied — the operation lacks the required permissions. 0x80070057 The parameter is incorrect — an operation received an invalid argument. 0x8007007B The filename, directory name or volume label syntax is incorrect. 0x80004005 Unspecified error — the catch-all Windows failure code. 0xC0000005 Access violation — a program read or wrote memory it does not own. 0x80070002 The system cannot find the file specified. 0x800F0922 A Windows update or optional feature failed to install (0x800F0922). 0x80073712 Windows Update failed because a required update component is missing or corrupted (0x80073712). 0x80070643 An update installation failed with a fatal error, most often a .NET Framework or security-intelligence update (0x80070643). 0x80072EE2 Windows Update timed out while trying to connect to the update servers (0x80072EE2). CRITICAL_PROCESS_DIED Blue screen: a process critical to Windows terminated unexpectedly. KERNEL_SECURITY_CHECK_FAILURE Blue screen: the kernel detected corruption of a critical data structure. IRQL_NOT_LESS_OR_EQUAL A blue-screen stop error (IRQL_NOT_LESS_OR_EQUAL) where a driver or kernel process accessed memory at an invalid IRQL. PAGE_FAULT_IN_NONPAGED_AREA A blue-screen stop error (PAGE_FAULT_IN_NONPAGED_AREA) where the system requested a page of memory that was not present. DPC_WATCHDOG_VIOLATION A blue-screen stop error (DPC_WATCHDOG_VIOLATION) where a driver spent too long at high priority and the watchdog timer expired. SYSTEM_SERVICE_EXCEPTION A blue-screen stop error (SYSTEM_SERVICE_EXCEPTION) triggered by an illegal instruction or memory access in kernel or driver code. INACCESSIBLE_BOOT_DEVICE A blue-screen stop error (INACCESSIBLE_BOOT_DEVICE) where Windows cannot read the disk it should boot from.

About Error Code Lookup

The Error Code Lookup is a searchable directory of more than 200 common error messages and codes across 12 categories: HTTP status codes, Windows error codes, browser and network errors, JavaScript, Python, PHP, Node.js and npm, Java, MySQL, Git, Linux shell errors and email/SMTP codes. Every entry is written in plain language for quick troubleshooting.

Each error is explained in three parts: what the message actually means, what usually causes it and concrete steps to fix it. That structure turns a cryptic string like ERR_CONNECTION_REFUSED or 0x80070005 into an actionable checklist instead of a guessing game.

You can filter the list by category, search by code, constant or message fragment, and copy any code with one click. Every error also has its own dedicated page with related errors from the same category, so you can bookmark or share a direct link to the exact fix.

How to use Error Code Lookup

  1. Type the error code or message into the search box — for example 404, ERR_NAME_NOT_RESOLVED or 0x80070005.
  2. Narrow the results with the category filter (HTTP, Windows, JavaScript, MySQL and so on) if the search returns too many entries.
  3. Open the matching entry to read what it means, its likely cause and how to fix it.
  4. Use the copy button to grab the exact code for a bug report or support ticket.
  5. Check the related errors section for other errors from the same category.

Frequently asked questions

It covers 12 categories: HTTP status codes, Windows system errors, browser and network errors, JavaScript, Python, PHP, Node.js and npm, Java, MySQL, Git, Linux shell errors and email/SMTP reply codes — more than 200 entries in total.

Search with fewer words. The shortest unique part works best: just the numeric code (“404”, “0x80070005”) or the constant name (“ERR_NAME_NOT_RESOLVED”) rather than the full sentence your system printed.

Yes. Each entry has a dedicated detail page explaining the meaning, likely cause and fix, plus related errors from the same category. You can bookmark it or send the link directly to a colleague or a support ticket.

The fixes describe the standard, widely accepted resolution for each error. Still, read the likely-cause section first — the same code can have several triggers, and matching the cause to your situation tells you which fix applies.

Yes, it is completely free. You can search, browse the category directory and open as many error detail pages as you need without an account.
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