Start clean
Keep the source untouched and open a copy as plain text.
GPX is XML, so its structure can be read in a plain-text editor. Make a copy first, especially when the file is the only record of an activity. Viewing text should not alter the route, but some editors can change character encoding, line endings or content when they save.
Check that the file came from a source you recognise and that its size is plausible before opening it in specialist software. A .gpx suffix is only a filename. It does not prove that the contents conform to GPX.
If the route reveals a home, workplace or private trip, avoid uploading it to an unknown online checker. Local inspection lets you examine structure without handing the coordinates to another service.
The outer structure
A GPX 1.1 document declares its root, version and creator.
Near the top, look for a <gpx> root element using the GPX 1.1 namespace. The official schema requires the version value 1.1 and a creator string naming the software that wrote the document.
Then identify the major child elements in document order:
<metadata>Optional information about the file, such as a name, description, time and geographic bounds.<wpt>Standalone waypoints or named features.<rte>Routes made from ordered route points.<trk>Tracks made from one or more segments of ordered track points.<extensions>Additional elements defined outside the core GPX namespace.
A file can be valid while containing no navigable line. Waypoints alone are useful positions, but they are not an ordered route or track.
The useful evidence
Read representative points and the boundaries around them.
- Count
Find every route, track and track segment.
This catches collection files and discontinuities that a single map preview can obscure.
- Sample
Read the first, middle and final point.
Latitude and longitude are required point attributes. Elevation, time, names and extensions are optional.
- Check
Confirm coordinate ranges and order.
GPX latitude must be between -90 and 90 degrees. Longitude starts at -180 and remains below 180 degrees.
- Scan
Look for repeated, missing or implausible attached values.
Repeated positions, reversed timestamps and sudden elevation steps may explain strange statistics.
- Map
Inspect the geometry visually as well.
Text proves structure. A map exposes wrong continents, straight gaps, unexpected branches and a reversed start more quickly.
What validation proves
Schema-valid and suitable are separate judgements.
An XML-aware validator can compare the document with the official GPX 1.1 schema. That catches structural faults such as missing required coordinates, invalid ranges, misplaced elements or a missing required creator attribute.
Validation cannot establish that the course follows a real path, that public access exists, that timestamps are truthful or that elevation values are accurate. It also cannot promise that a particular app supports every valid extension or every combination of routes and tracks.
Use validation to answer “is this structured as GPX?” Use the map and source evidence to answer “is this the route I intend to use?”
Sources & scope
What this answer is based on.
The sources define XML and GPX structure. The privacy advice limits unnecessary sharing; it is not a security certification of any editor, validator or downloaded file.