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What GetCapabilities tells you about a WMS or WFS

The short answer: it is the service's own menu. Append ?SERVICE=WMS&REQUEST=GetCapabilities&VERSION=1.3.0 to the service URL and you get an XML document listing every layer, projection, and format it will give you.

It looks intimidating, and it is usually thousands of lines. But there are only four things in it worth reading.

Asking for it

https://example.com/geoserver/wms?SERVICE=WMS&REQUEST=GetCapabilities&VERSION=1.3.0
https://example.com/geoserver/wfs?SERVICE=WFS&REQUEST=GetCapabilities&VERSION=2.0.0
https://example.com/wmts?SERVICE=WMTS&REQUEST=GetCapabilities&VERSION=1.0.0

Three parameters, always: what kind of service, what you want, and which version. Get the version wrong and some servers argue, so those are the safe ones.

Open it in a browser. Every browser will pretty-print XML and let you collapse the branches, which makes it far more manageable than it first looks.

The four things worth reading

1. The layer names

This is why you came. Inside each <Layer> there are two things that matter:

<Layer queryable="1">
  <Name>council:flood_zones_2024</Name>
  <Title>Flood Hazard Zones (2024)</Title>

<Name> is what you pass to the server. <Title> is what humans read. They are almost never the same, and the viewer showed you the Title. If you have been trying to request Flood Hazard Zones (2024) and getting errors, this is why.

queryable="1" means you can click a feature and get its attributes back via GetFeatureInfo. Worth noting: it tells you the service knows more than it is drawing.

2. What projections it will give you

<CRS>EPSG:4326</CRS>
<CRS>EPSG:3857</CRS>
<CRS>EPSG:2193</CRS>

Ask for one that is not on this list and you get an error. If you need data in a local projection and the service only offers web mercator, you reproject it yourself afterwards, which is fine but worth knowing before you start.

3. Where the data actually is

<EX_GeographicBoundingBox>
  <westBoundLongitude>166.4</westBoundLongitude>
  <eastBoundLongitude>178.6</eastBoundLongitude>
  <southBoundLatitude>-47.3</southBoundLatitude>
  <northBoundLatitude>-34.4</northBoundLatitude>
</EX_GeographicBoundingBox>

The bounding box saves you the classic twenty minutes of staring at an empty map wondering why nothing is drawing, when in fact you are looking at the wrong hemisphere.

4. What formats you can have

For WMS, the GetMap section lists image formats. For WFS, the GetFeature section lists output formats, and this is the important one:

<Operation name="GetFeature">
  <Parameter name="outputFormat">
    <Value>application/json</Value>
    <Value>application/gml+xml; version=3.2</Value>
    <Value>SHAPE-ZIP</Value>

If application/json is there, you can have GeoJSON, and life is easy. If it is GML only, you get GML, and QGIS will read it happily even though you would rather it did not. SHAPE-ZIP means the server will build you a shapefile on demand, which is a nice thing to discover.

The bit people miss

The capabilities document routinely lists layers the public viewer never showed you.

A council viewer might expose three layers. The service behind it publishes forty: historic aerials, zoning, contours, the stormwater network. All equally public, all equally fetchable, none of them linked from anywhere.

That is not a security hole. The service was configured to publish them; the viewer was just curated for a particular audience. But it does mean the capabilities document is frequently a far better catalogue of an organisation's data than its actual data portal.

Why you rarely need to read one by hand

The document exists so software can read it. QGIS reads it when you add a connection, which is why the layer list appears.

Geo Hound reads it too, automatically, the moment it detects a service while you browse. The title, provider, abstract, layer list, keywords, coordinate systems, and bounding box on a service card all come straight out of the capabilities document, which means you get the useful four things without opening the XML at all.

Then it hands you the URL with the right GetCapabilities request and version already attached, formatted for QGIS or ArcGIS Pro.