What is the ETL file format?
.etl file format is used for storing event logs created by the Windows Event Tracing for Windows (ETW) subsystem. It stores data in binary format. Logs are generated by ETW providers - kernel, system, and application components that instrument their activity - rather than by a single tool. The ETW framework logs such events as:
- Disk access
- Page faults and memory operations
- Memory stack operations
- Application events and custom provider messages
A trace session can also include system startup and shutdown events. Because .etl files store data in a proprietary binary format, dedicated diagnostics and reporting tools are required to read them. .etl files should not be edited manually.
.etl files store logs of high-frequency events along with their descriptions and timestamps. Such files can be helpful during system troubleshooting and performance analysis. Before the system events are written to an .etl file, they are buffered in memory and then flushed to disk in compact binary format to keep overhead low. Report files can take a large amount of space, so it is advised to track the amount of available disk space when running long trace sessions. The tracerpt command can be used to parse event trace logs and convert them to readable formats, while Windows Performance Analyzer (WPA) and the open-source PerfView tool offer graphical views and advanced filtering. Related log formats include .evtx (modern Windows Event Log) and .blg (Performance Monitor binary log).
Security & safety
RISK: LOWAn .etl is passive trace data, not executable, so it can't 'run' anything by itself. Two real considerations: (1) privacy - a trace can capture sensitive details (file paths, URLs, process names, sometimes network or credential-adjacent data), so be careful about sharing an .etl publicly; only send traces to trusted support channels. (2) Disk space - Windows-generated ETLs (e.g. in LogFiles\WMI, WPR captures) can grow large; most are safe to delete if you don't need them, and Windows will recreate active ones. Don't delete ETLs that a running trace session is currently writing to.
Format details
in a nutshellPrograms that open ETL files
Windows5 apps
Event Viewer
Built-in Open Event Viewer > Action > Open Saved Log, pick the .etl; it displays the events and can convert/save them to .evtx. Quickest free look, no install.
Windows Performance Analyzer (WPA)
Free Install the Windows Performance Toolkit (part of the Windows ADK, or from the Microsoft Store), then File > Open the .etl for graphical CPU/disk/boot timeline analysis.
PerfView
Open-source Free Microsoft profiler: launch PerfView.exe, double-click the .etl, then Events to browse traces (great for CPU/.NET analysis).
tracerpt (command line)
Built-in Run in an admin prompt: tracerpt yourfile.etl - outputs dumpfile.xml and summary.txt (add -of CSV for CSV). Built into Windows; best for getting readable text.
Microsoft Message Analyzer (legacy network traces)
Free Older tool for network/protocol ETL traces. RETIRED by Microsoft (download removed Nov 2019) - use WPA/PerfView or PktMon instead; mention only for legacy captures. Technical details
deep spec| Developer | Microsoft |
| Format type | Binary ETW (Event Tracing for Windows) trace log |
| Platform | Windows only (ETW is a Windows-exclusive subsystem) |
| Introduced | Windows 2000 (ETW first shipped with Windows 2000) |
| Header structure | Internal WMI logfile header event record at the start of the file; no fixed-length ASCII magic bytes |
| MIME type | application/octet-stream |
| Encoding | Binary (not human-readable; requires ETW-aware tools) |
| Buffering mechanism | Events are collected in per-CPU in-memory buffers before being flushed to disk |
| Event coverage | Kernel, driver, system service, and user-mode application events via registered ETW providers |
| Primary command-line tool | tracerpt - built into Windows; converts .etl to CSV or XML report |
| GUI analysis tools | Windows Performance Analyzer (WPA) and open-source PerfView |
| Output formats via tracerpt | CSV summary and XML event report (REPORT.XML + SUMMARY.TXT) |
| Log file mode | Supports sequential (linear) and circular (wrap-on-full) file modes |
| Real-time streaming | ETW sessions can deliver events to a real-time consumer in addition to, or instead of, a file |
| Related log formats | .evtx (Windows Event Log), .evt (legacy Event Log), .etlx (extended ETL), .blg (Performance Monitor) |
| Released | Windows 2000 (Event Tracing for Windows / ETW) |
| Specification | learn.microsoft.com |
ETL conversions
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