Working with large log files has always been a pain point for me as a developer. Files over hundreds of megabytes — sometimes gigabytes — would freeze or crash editors like Notepad++ or IDEs. Searching, filtering, or summarizing them was slow and frustrating, and scripting ad-hoc solutions took time and often failed on edge cases.
To solve this problem, I built FastLog, a Windows-native command-line tool optimized for speed and low memory usage. FastLog reads logs incrementally, processes them line by line, and provides fast filtering by log level, time, and keywords. For multi-GB logs, the Pro version supports multi-threaded processing and JSON export.
The free version is fully usable for everyday debugging:
- Shows the top 50 results
- Single-threaded processing
- Ideal for quick inspection
Example usage:
fastlog analyze server.log --level ERROR
The free version is easy to try, requires no installation, and has no external dependencies. The Pro version removes limits, runs faster on very large files, and allows exporting results to JSON for further analysis or automation.
FastLog started as a personal project, but I decided to share it publicly so others who work with large logs can benefit. Feedback and suggestions are welcome — both technical and usability-related — as they directly influence future improvements.
For anyone interested in trying it out: https://dmykytenko.itch.io/fastlog
And the Pro version is available on the same page for those who need full functionality.
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