GPX viewer

GPX is the GPS Exchange Format, written by Dan Foster at TopoGrafix. Version 1.1 arrived in 2004 and that’s where it stopped. Twenty years without a new version is unusual, and it’s why GPX works everywhere: Garmin, Wahoo, Strava, Komoot, OS Maps, a decade-old handheld in a drawer. Everyone implemented it once and nobody moved the goalposts.

Inside, it’s XML holding three kinds of thing. People mix them up constantly, and the difference changes what you should do with the file.

<wpt>

A waypoint. One marked spot with a name: a car park, a water stop, the gate you keep missing. Each one opens here as a marker you can drag or rename.

<trk>

A track. The breadcrumb trail of where you actually went, logged by the device every second or few seconds. Tracks are split into segments, and each segment opens as its own line.

<rte>

A route. A plan rather than a record: a short list of turn points you intend to follow. Komoot and plotting sites sometimes hand you one of these instead of a track. It opens as a line too.

All three open here. A file can hold any mix of them, and plenty hold all three at once: a planned route, the track you actually recorded following it, and the waypoints you dropped along the way.

Positions and names. That’s the lot. Every track point’s latitude and longitude comes through, the track or waypoint name becomes the label, and everything else in the file is discarded on import.

The discarded pile is long: <ele> elevation, <time> timestamps, and the whole extensions block where Garmin stashes heart rate, cadence, power and temperature. Also descriptions, symbols, link tags and the accuracy fields like hdop. Which means no elevation profile here, no average speed, no splits, no calories.

That’s a real limitation and worth stating before you waste ten minutes looking for the chart. For analysing a ride, use the app that recorded it. What this is good for is the geometry: seeing where a track actually goes, measuring its length, comparing two of them on one map, cleaning up the bits that are wrong.

One practical consequence. If you export GPX from here, the file that comes out has no elevation and no times, because they were gone before you touched anything. Fine for loading a route onto a device to follow. Not something to send to Strava and expect your climbing total back.

Almost every recorded track has rubbish at the start. The watch is still finding satellites while you stand in the car park, so the first thirty seconds wander across a field at an implausible speed. Some devices add a point at 0,0 before they get a fix, which drags the whole map out to the Atlantic.

Load the file, switch to Select, click the track, and drag or delete the offending points. Then export. The same job in a desktop GIS is a twenty-minute detour.

Same move for privacy. Drag the first few points away from your front door before you share a ride. Nothing was uploaded, so the trimmed file is the only copy that exists.

A one-second recording generates 3,600 points an hour. A long ride can be forty or fifty thousand, and a multi-day walk logged on a phone can run past a hundred thousand. The map will draw those. Editing them is another matter, since every point becomes a draggable vertex, and the browser starts to feel it.

The share link has a hard ceiling, too. It encodes the whole drawing into the URL rather than storing anything server-side, and a dense track won’t fit. You get told, and pointed at the GeoJSON download instead. Coordinates in a link are also rounded to five decimal places, about a metre, which is below GPS accuracy anyway but worth knowing if you’re comparing exports.

GeoJSON if it’s heading into a web map or a script. KML to open it in Google Earth, which draws a track nicely draped over terrain. CSV for a spreadsheet, though that only takes markers, so a track has nowhere to go. GPX back out if you just wanted to tidy it.

Going the other way works as well: drop a GeoJSON or KML file on the map and export it as GPX for a device. A polygon converts to a closed track, since GPX has no idea what an area is.

There are plenty. gpx.studio is excellent and does elevation properly. Strava, Garmin Connect and Komoot all render a file you upload. We’re not claiming to have beaten any of them at what they do.

Two differences, both narrow. Your file isn’t uploaded: it’s read in the browser and drawn there, so nobody gets a copy of your movements in exchange for looking at them. For a GPS track that’s a stronger argument than it is for most file types.

And the track is editable the moment it loads, in the same tab, with undo. Drag a point, cut a section, relabel it, add a marker where the gate was, then export or share a link. Most viewers render and stop there.