GPX Editor — Power & Speed

GPX Editor is a standalone web application for editing GPX files of cycling activities (natively compatible with Garmin Connect and Strava). All processing happens locally in the browser: your data never leaves your computer.

Key Features

• Zero server dependencies: Works 100% offline.
• Activity Dashboard: Instant display of 6 KPIs (Average Power, Average Speed, Distance, Duration, Trackpoints, Elevation +).
• Profile Chart: Elevation profile and overlaid power via Chart.js.
• Proportional Edit:
  • Watts: Scales all power data based on a target average.
  • Speed: Compresses or stretches timestamps to reach the desired average speed without altering GPS coordinates.
• Export: Download the modified file ready for re-import.
• Dark/Light Mode: Support for light and dark themes.

Getting Started

1. Open index.html in your browser.
2. Drag a .gpx file into the upload area.
3. Select the edit mode (Watts, Speed, or both).
4. Enter the target values.
5. Click "Export" to download the new file.

Technical Notes

• The app uses the browser's native XML parser.
• Charts are automatically sampled to ensure smooth performance even with very large files.
• If the original file contains no power data, Watts-related options will be disabled or flagged.

Privacy

The app does not send data to external servers. Files are read locally via the FileReader API and processed in memory.