BLG File

What are BLG files and how to open them

Are you having problems opening a BLG file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BLG files.

What is a BLG file?

A .BLG file is a Microsoft Windows Performance Monitor Binary Log file.

Microsoft Windows Performance Monitor Binary Log is a proprietary format used by Windows Performance Monitor to record system performance data over time. It's produced when Performance Monitor or command-line tools (such as logman or typeperf) are used to track performance counters - such as CPU, memory, disk, network usage - and collect those metrics continuously or at set intervals. The log serves for diagnosing system behavior, locating resource bottlenecks, analyzing trends, and troubleshooting issues.

The binary log file is written in a format that is efficient for recording large volumes of data and designed for later reading and analysis rather than immediate human readability. Performance Monitor and similar tools write data into it; afterward it can be opened directly in Performance Monitor, converted to text (like CSV) using the relog command-line tool, or imported into other analysis tools. Users define which counters to record and how often; the file may stop or wrap when it reaches a size limit, depending on configuration.

Files in this format begin with a binary header and contain structured records for each sample of each performance counter. An internal identifier can be observed: for example, at offset 180 there is a string referencing "tzres.dll," along with other recognizable keywords like "TOTAL" and "BLG." The header contains fields that specify, among other things, the file type, version, and timestamp.

How to open BLG files

Important: Different programs may use files with the BLG file extension for different purposes, so unless you are sure which format your BLG file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested four different BLG openers which you will find listed below.

Last updated: August 24, 2026

Various apps that use files with this extension

These apps are known to open certain types of BLG files. Remember, different programs may use BLG files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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