GPX viewer — open a GPX file and read what is actually inside it.

Check the climb before you ride the route.

A route file says how long it is; it rarely says how much of it goes up. The gain figure here is the sum of the rises in the profile, so a 60 km loop with 1,800 m of climbing reads very differently from a flat 60 km. Read it before deciding on gearing, or on how much water to carry.

Preview a route someone sent you before it goes on your device.

Files arrive by message and by email. Opening one here shows the shape, the distance, and the climb before anything is copied onto a watch — so a route that starts 40 km from where you expected is caught on a laptop screen rather than at a trailhead.

See where a recording went wrong.

A track recorded under trees or between buildings wanders, and the line shows it. Zoom in on the suspect stretch: a spur that leaves the road and returns is a bad fix, not a detour. Seeing that as a line is faster than reading a list of coordinates, and faster than scrolling a graph of speed.

Inspect a Strava or Komoot export before importing it.

Exports from activity apps arrive as GPX, and the point count varies a lot between them. This viewer reports how many points the file holds, which tells you whether you are looking at a dense recording or a thinned route. A file with 40 points over 80 km is a set of instructions, not a recording. They also differ in whether they carry elevation at all: a route exported from a planning tool often has none, while the same route exported from a device that rode it does.

Compare the distance a file claims with the distance you will ride.

The distance shown is measured along the points in the file, not read from a metadata field. If a route is described as 100 km and the line measures 94 km, the difference is in the file — usually a straight line drawn across a section nobody recorded.

Check a paused recording that split into several segments.

Recording apps start a new segment every time you pause. This viewer reads every segment in the file and draws them as one line, so a ride recorded in four parts shows its real length instead of only its first part. That is also why a track with a gap in it can still measure the full distance.

Verify a course that is already on your Garmin.

Export the course back out of Garmin Connect and open it here. If the line is the one you planned, the device has the right file. If it is a straight line between two towns, the import took the endpoints and dropped the shape. The Garmin guide covers that round trip.

A GPX file can hold more than a line, and this viewer is deliberately narrow: it reads the points, the heights, and the name, and ignores the rest. Knowing what is ignored explains most surprises.

Version matters less than people expect. A GPX 1.0 file puts the name and description at the top level; GPX 1.1 moved them into a metadata block. This viewer looks for the name in the first track, then the first route, then the metadata block, so both versions open. What it does not do is convert between them — a file read here is written back out as GPX 1.1.

GPX is the interchange format: XML, open, and read by almost everything. KML is Google Earth’s format and the one Google My Maps writes; it carries styling and folders, and it is what you get when you export a map rather than a track. KMZ is a zipped KML.

TCX is Garmin’s XML format for courses and activities, and it is the only one of these that can carry a course cue sheet. FIT is the binary format Garmin devices record natively — the smallest of the four, and not human-readable.

This page reads GPX only. KML and KMZ go through the KML converter, which reads both and writes GPX.

Choose GPX when the next thing to open the file is a device or an app. Choose KML when the next thing to open it is a person looking at a map. Choose TCX or FIT only when the destination demands them, because fewer tools can read those back.

Open a track and the toolbar reports the elevation gain beside the distance and the point count. A file with fewer than two heights has no gain to report, and the row stays empty. The profile at the bottom of the map plots height against distance along the route, so a climb early in the line is not hidden inside a total.

Elevation gain is the sum of the upward parts of that profile. A rise counts only when it is more than one metre above the point before it; anything smaller is skipped. That rule keeps GPS jitter and rounded spot heights out of the number, so the total stays on the low side rather than inflated.

If the file carries no elevation, the map samples terrain data and fills in an estimate for every point, so a flat-looking file can still show a profile. The tiles are public Terrarium terrain, sampled at zoom 12, where one tile pixel covers roughly 40 metres on the ground at the equator. Treat those numbers as estimates — they come from a terrain model, not from a barometer and not from survey data.

Where the heights come from changes what the number means. A barometric altimeter, which most watches and phones carry, tracks air pressure and drifts with the weather. A GPS-only height is the weakest of the three. Terrain data is a model of the ground rather than a record of where you were, so it cannot see a bridge, a tunnel, or a building. The shape of the profile is more reliable than any single height on it.

The sampling interval matters as much as the heights. A file with a point every second holds more small rises than the same route thinned to a point every ten seconds, so a denser file usually reports a higher total even under the same threshold rule.

Zoom before you judge the shape.

At country scale, every route looks like a clean curve. Zoom to street level and the question you actually have — did this route take the bridge or the ferry — becomes answerable. The line is the data; the zoom is the question.

Read the profile, not the total.

Two routes with the same 900 m of climbing can feel nothing alike. One climbs steadily and one puts the same 900 m into a single 6 km wall. The profile shows which one you have; the total does not.

Trust the point count over the name.

A file called “final-route-v3” may hold 30 points. The count tells you whether you have a recording or a sketch. Below about 50 points for a day route, expect straight lines between corners.

A long straight line usually means a missing section.

Devices lose signal in tunnels, in valleys, and on a plane. When they do, some apps write a straight line between the last fix and the next one. If a route cuts across a lake, that is what happened, and the distance is understated.

Compare two files before you pick one.

Open the first, note the distance and the point count, then open the second. Two exports of the same ride often differ: one from the watch, one from the phone, one already smoothed by an app. The file with more points is not automatically the better one — it is the one with more noise in it.