TrailToolbox: Local Sport File Converter

Browser-only conversion and repair for runners' and cyclists' track files

Problem

Runners and cyclists accumulate FIT/GPX/TCX files across Garmin, Strava, and other platforms; uploads get rejected across services, activities need merging, and corrupted FIT files won't open. Existing online tools require uploading files containing complete travel records to unknown servers, which feels unsafe.

Solution

All parsing and conversion run locally in the browser — no upload, works offline. Supports the FIT/GPX/TCX/KML/GeoJSON conversion matrix preserving heart rate, cadence, and power, plus activity merge/split, corrupted-file repair, and Google Timeline JSON import.

Users

Runners, cyclists, hikers, and anyone migrating workout data in bulk

MVP

FIT/GPX/TCX three-way conversion preserving sensor fields; merge/split FIT activities; basic corrupted FIT repair; fully local with zero upload; free and no signup

Revenue

Free core builds trust; a one-time Pro unlock for batch processing, large files, presets, and a CLI version; affiliate links in cycling/running communities

Why now

Wearable and platform ecosystems are increasingly fragmented with steady migration demand; browser-side WASM/JS is now fast enough for a solo maintainer