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OSM UK Address & Postcode Mapping

For background on how postcodes work in the UK, please see Wikipedia: Postcodes in the United Kingdom. For details of the structure of UK addresses see the "Programmers' Guide" on Royal Mail's Powered by PAF website.

Tools and Reports

OSM Postcode Mapping Stats
Details of the number of postcode units mapped in each postal area and district.
OSM Street Name Warnings
Possible errors in addr:street and names of associatedStreet relations for OSM objects with postcodes.
Post Town Warnings
Possible errors in the Post Town (addr:city) tagging of OSM objects with postcodes.
OSM Postcode Value Errors
List of erroneous addr:postcode values found in OpenStreetMap data for the UK.
OSM Overfull Postcode Units
List of postcodes where there are more than 100 OSM objects objects with the same postcode. This generally shouldn't happen as each postcode unit contains at most 100 delivery points.
OSM Postcode Offsets (Location Discrepancies)
List of OSM objects where there is a discrepancy between the object's location and the centroid of its addr:postcode from Code-Point Open.
UPRN Locations (beta)
Map showing the locations assigned to each of the 38 million Unique Property Reference Numbers in Great Britain, as released in the new OS Open UPRN dataset.
History of OSM Postcode Progress
Various graphs showing the numbers of GB postcodes and postcode errors in OSM over time.
Address Tag (addr:*) Usage Report
Tables showing the current number of uses of different addr:* tags in Great Britain.

Resources for Postcode Mapping

Code-Point Open
Official UK data from Ordnance survey, available for re-use under the Open Government Licence v3 (hence suitable for use in OSM). Includes all postcodes, but only includes a single centroid location for each unit. The centroids are usually calculated by taking the arithmetical mean of the coordinates of each address point with that postcode, and then snapping this to the nearest address point with that postcode. But things are actually slightly more complicated than this — see Algorithm for Computing Postcode Centroids in Code-Point Open.
National Statistics Postcode Lookup & ONS Postcode Directory
Two Open Data products from the Office for National Statistics. They contain a list of postcodes with the Code-Point Open Centroids, and then relate the postcode units to other statistical geographies. In terms of OSM use, there are a couple of advantages over Code-Point Open: old postcode units are also included, along with fields for user type date of introduction and date of termination. ONS has confirmed that this additional information can all be used under the Open Government Licence.
Ragged Red: Displaying Code-point postcode centroids
Details of tiles displaying Code-Point Open Centroids, that can be loaded in OSM editors, or shown on the OS Compare Map.
Food Hygiene Open Data OpenStreetMap Tool
Tool for comparing mapping of food outlets with official hygiene rating data. A useful source of addresses and for flagging when previously mapped premises have closed.
New Postcodes
Map showing newly created postcodes. Useful in well-mapped areas, where people want to check the new developments are being added to OSM.
British Postcodes on OpenStreetMap
Blog post from 2013.
Overpass Turbo Queries
OSM Inspector: Addresses
Geofabrik's tool to identify objects with address tags, and flag potential issues.