What is the WER file format?
A .wer file is a Windows Error Report generated by the Windows Error Reporting (WER) service, a component built into Windows Vista and all later releases by Microsoft. The .wer file is a plain-text file that captures error information for both application crashes and operating-system faults that have occurred on the machine.
The file uses an INI-like structure - [WER...] section headers followed by Key=Value lines - and is typically encoded in UTF-16 LE (little-endian), beginning with the byte-order mark FF FE. It records fields such as the faulting application name and version, the module that triggered the fault, the OS build number, the exception code, and bucket parameters used by Microsoft's crash-analysis back end.
Importantly, the .wer file is the human-readable metadata for a crash, not the crash data itself. The actual memory snapshot lives in companion .mdmp and .hdmp files stored in the same report folder. When used in combination, the .wer metadata and the minidump files together provide the information needed to diagnose the cause of the crash.
The .wer file is generally stored at the following locations on Windows:
C:\Users\<USER>\AppData\Local\Microsoft\Windows\WER\ReportQueueC:\Users\<USER>\AppData\Local\Microsoft\Windows\WER\ReportArchiveC:\ProgramData\Microsoft\Windows\WER\ReportQueueC:\ProgramData\Microsoft\Windows\WER\ReportArchive
The files can be opened with any text editor such as Notepad, or reviewed via Windows Event Viewer.
Security & safety
RISK: LOWWER files are harmless plain-text logs - they cannot execute and contain no document content. They are safe to delete (Windows recreates them as needed); Disk Cleanup and Storage Sense remove them under "Windows Error Reporting Files". One minor privacy note: a report can include the full path of the crashed program and, for some events, snippets of in-memory strings, so avoid posting raw WER/dump files publicly. The only real-world "risk" is being tricked by fake "error report" pop-ups or scam tools promising to "fix .wer errors" - the file is a symptom report, not something that needs repairing.
Format details
in a nutshell- WERCONFIG / WER internal metadata - Some WER folders contain Report.wer alongside WERInternalMetadata.xml and triage .txt files for the same crash event.
Programs that open WER files
Windows2 apps
Notepad
Open-source Open the file; it auto-detects UTF-16 encoding and shows the sections clearly. Better for long reports than Notepad. 
Event Viewer
Built-in Not for the .wer file itself: open eventvwr.msc > Windows Logs > Application to see the same crash events with context. Reliability Monitor (perfmon /rel) shows a friendly timeline. Technical details
deep spec| Encoding | UTF-16 LE (little-endian) with BOM FF FE; occasionally ASCII or UTF-8 without BOM |
| Magic bytes | FF FE at offset 0 (UTF-16 LE BOM); no fixed binary signature - first readable text is typically "Version=1" or a "[" section header |
| File structure | INI-like plain text: [WER...] section headers followed by Key=Value lines |
| Internal version field | "Version=1" present at the top of the report body |
| MIME type | text/plain |
| Typical file size | 1 KB - 30 KB |
| Developer | Microsoft |
| Associated OS | Windows Vista, 7, 8, 10, 11 and Windows Server editions |
| Default storage paths | %LOCALAPPDATA%\Microsoft\Windows\WER and %ProgramData%\Microsoft\Windows\WER (ReportQueue and ReportArchive subfolders) |
| Companion file types | .mdmp and .hdmp minidump files co-located in the same report folder; may also include .etl event trace logs |
| Generation process | Created automatically by WerFault.exe or WerFaultSecure.exe when an application or system fault is detected |
| Key recorded fields | Faulting application name, version, module path, OS build, exception code, and bucket ID for Microsoft crash analysis |
| Compression | None - stored as uncompressed plain text |
| Report lifecycle | Reports land first in ReportQueue (pending upload); moved to ReportArchive after submission or local retention |
| Released | 2006 (Windows Error Reporting redesigned in Windows Vista) |
| Latest version | Windows Error Reporting (current in Windows 11; format unchanged since Vista) |
| Specification | learn.microsoft.com |
WER conversions
Community Q&A
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