How is this different from the GPX Track Viewer/Distance tools?

Those tools only read track points for track-specific stats; this converter also reads waypoints and routes, and its only output is plain GeoJSON.

Does this include elevation?

Yes, when present - elevation is kept as each point’s coordinate z-value.

Convert a GPX file (GPS track/waypoints) to GeoJSON, in your browser.

Input (GPX)

Output (GeoJSON)

KML/GPX parsing only runs in the browser.

Runs entirely in your browser - nothing is sent to a server.

How is this different from the GPX Track Viewer/Distance tools?: Those tools only read <trkpt> track points for track-specific stats; this converter also reads <wpt> waypoints and <rte> routes, and its only output is plain GeoJSON.
Does this include elevation?: Yes, when present - elevation is kept as each point’s coordinate z-value.