json2fit

Free local-first tool for migrating Polar Flow exports to Garmin Connect.

What it does

• Converts Polar Flow ZIP/JSON exports to Garmin-friendly TCX/FIT files.
• Runs locally in the browser.
• Does not upload training data to any server.
• Requires no account.

Live app

https://0x00.com.pl/tools/json2fit/

Privacy

Your files are processed locally in your browser. The app does not require an account and does not upload Polar Flow exports, GPS tracks or workout data to a backend.

Supported exports

• Polar Flow ZIP export
• Polar Flow JSON files
• Training sessions
• TCX/FIT export
• Experimental CSV export for daily activity and wellness reports

How to use

1. Export your data from Polar Flow.
2. Open json2fit.
3. Select the ZIP file or JSON files.
4. Review detected activities.
5. Export TCX/FIT files.
6. Import generated files into Garmin Connect.

Development

Use npm, as indicated by package-lock.json.

npm install
npm start

Build:

npm run build

Run tests:

npm run test
uv run pytest

Disclaimer

This project is not affiliated with Polar, Garmin or Fitbit.

License

MIT