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A WMS request refers to an HTTP request made to a Web Map Service (WMS) server, defined by the Open Geospatial Consortium. It asks the server to generate a map image or provide metadata for geographic data. A WMS request typically includes the service parameter set to WMS, a request parameter that names the operation, a version, and other parameters that describe layers, area, and format. The common request types are GetCapabilities, GetMap, GetFeatureInfo, and GetLegendGraphic.

GetCapabilities returns an XML document describing the available layers, supported output formats, styles, and service operations. GetMap is the primary operation used to obtain a rendered map image of one or more layers. GetFeatureInfo allows retrieval of attribute information for features at a clicked location on a rendered map. GetLegendGraphic provides a legend image for one or more layers.

Key parameters for a GetMap request include: layers (a comma-separated list), styles (one style per layer), format (for example image/png or image/jpeg), transparent (true or false), width and height (in pixels), and bbox defining the map extent. In WMS 1.3.0, the coordinate reference system is specified with CRS, whereas earlier versions used SRS; axis order may vary by CRS. Other requests use variations of these parameters but generally preserve the service and request identifiers.

Requests can be sent via HTTP GET, and POST is also supported for longer or more complex requests. The server’s response varies by operation, typically an image for GetMap or an XML document for GetCapabilities. WMS requests support interoperable map rendering across GIS clients and web applications and are a core part of many spatial data infrastructures.