Offline, privacy-focused HAR analysis tool built with FastAPI + vanilla HTML/CSS/JS.
Designed for support workflows on large HAR files (120k+ entries):
- fast filtering
- endpoint aggregation
- safe-mode masking (privacy)
- request detail inspection
- cURL export (only when safe mode is OFF)
When a customer sends a HAR, you typically want to answer quickly:
- “What are the top failing requests (4xx/5xx)?”
- “Which endpoints have the worst error rate?”
- “Are there slow requests (>1s)?”
- “Can I reproduce this request with a cURL?”
This tool is built to make that triage fast and safe, even on big captures.
- Masks query parameters
- Redacts sensitive headers
- Disables Copy as cURL when enabled
- Server-side filtering
- Pagination (avoids huge DOM rendering)
- Endpoint aggregation (count/errors/error rate/avg/p95/max)
Quick filters:
- Errors
- 5xx
- 4xx
- Slow (> 1s)
- 401/403
Advanced filters:
- host, method, type
- status range, min duration
- sorting
- auto-apply with debounce
- Click a request → full normalized JSON details
- Highlighting for 4xx / 5xx / slow / auth
- Copy as cURL (safe mode OFF only)
app/ (FastAPI backend + HAR parsing/analytics) web/ (static frontend, vanilla JS)
- Click Load a HAR
- Keep Safe mode enabled by default
- Click Load
- Use quick filters (5xx/4xx/Slow/401-403)
- Click an endpoint row to focus requests
- Click a request to inspect the full details
To copy cURL:
- Disable Safe mode
- Reload the HAR
- Select a request
- Click Copy as cURL
Because the executable is not code-signed, Windows may show a SmartScreen warning the first time you run it.
Steps:
- Click More info
- Click Run anyway
If your company environment blocks unknown executables, ask IT to whitelist the file hash or the release ZIP.
PowerShell (Windows):
python -m venv .venv Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass ..venv\Scripts\Activate.ps1 pip install -r requirements.txt python -m app.launcher
The recommended distribution is a Windows standalone executable built with PyInstaller.
End-users workflow:
- Download the zip from GitHub Releases
- Double-click HAR-Visualizer.exe
- The app opens in the browser automatically
- CSV export (filtered entries + endpoints)
- Error clustering (top repeated failures)
- Shareable support report (copy/paste summary)
- Optional response preview (size-limited)
MIT
Lucas Gourmelon GitHub: https://github.com/Leidvor