The WIGOS Data Quality Monitoring System (WDQMS) web tool is the result of the efforts by the ICG-WIGOS Task Team on WDQMS and of ECMWF (Prates and Richardson 2016) who further developed the web tool and hosts it, with the support of MeteoSwiss and the WMO Secretariat (WMO, 2019). The operational version of WDQMS web tool provides NWP-based monitoring of land-based surface and upper-air (radiosonde) observations. The monitoring categories, availability and quality, are based on near-real-time monitoring information provided by the four participating global numerical weather prediction (NWP) centres: the German Weather Service (DWD), the European Centre for Medium range Weather Forecasts (ECMWF), the Japan Meteorological Agency (JMA) and the US National Centers for Environmental Prediction (NCEP). The system aggregates the NWP monitoring information by station, time interval, observed variable and NWP Centre and generates availability and quality performance reports that are displayed as maps or time series. This User Guide is organized according to the entries and options available on the control panel of WDQMS web tool to facilitate the users search of a particular option. Information on the NWP-based monitoring options as well as on Monitoring categories are described in sections 2 and 3, respectively. Details of the temporal aggregation is given in section 4, and about NWP Centres in section 5. Finally, a summary of the products (maps and time series) available for the two main observation type categories covered by the tool is presented in section 6 and a list of Frequently Asked Questions (FAQs) and answers regarding WDQMS web tool are included in section 7.