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How to Open an ETL File on Windows

View formatted WPP messages from a .etl trace log.

What Is an ETL File?

An ETL file (Event Trace Log, .etl) is the binary log format produced by Event Tracing for Windows (ETW). When a Windows driver or application emits WPP or ETW events to a file-based session, the events are written to an ETL file. The data is compact and binary, so you need a trace viewer plus decode metadata (TMF files or PDB symbols) to turn it back into readable messages.

Open an ETL File, Step by Step

  1. Get WppViewer. Download the WppViewer demo or use a licensed WppViewer Studio build. The demo can open ETL files and display formatted WPP events.
  2. Open the ETL file. Launch WppViewer and open the .etl log file. WppViewer reads the events recorded by the trace session and lists them in the event view.
  3. Add TMF or PDB decode metadata. Point WppViewer at the TMF files or PDB symbols produced by the traced component so binary WPP payloads are formatted into readable messages.
  4. Filter and search the events. Use field filters, highlighting, and search to narrow the log to the provider, level, or text you care about.
  5. Inspect source and stacks. With a licensed Studio build, view source beside an event and inspect call stacks for ETW and DbgPrint events to move from a trace row toward the code path that produced it.
Download the demoSee WppViewer Studio

Why Messages May Look Unformatted

If you open an ETL file and see raw or unformatted WPP entries, WppViewer does not yet have the decode metadata for that provider. WPP messages are formatted using TMF files or the PDB for the build that produced the trace. Add the matching TMF/PDB path and reload the trace. For a full checklist, see WPP traces not showing.

ETL files are also how teams share traces: capture once, send the .etl, and open it on another machine. WppViewer keeps the workflow close to WDK TraceView while adding source, stacks, and filtering for faster analysis.