My ZIP codes don't match the geocodes in Datawrapper choropleth map

You've chosen a map of ZIP Code or Postal Code/Area from the base map library in Datawrapper

and you notice a mismatch between the ZIP codes in your dataset and Zip codes in the Datawrapper base map. If you're wondering why this article will hopefully help you understand what's going on and how to solve the issue. 

What is a ZIP code? 

A ZIP code is a type of postal code used by the US Postal Service to deliver mail and packages more efficiently. In most cases, addresses within close geographic proximity are grouped under the same ZIP code which gives the false impression that ZIP codes are geographic areas. A ZIP code is in fact a collection of delivery routes to points of delivery and is not a geographical area. You can find a detailed explanation on unitedstateszipcodes.org. 

Because there's no clear geographic boundary for a ZIP code, there is no official map of ZIP codes. ZIP code maps in the Datawrapper library are taken from third-party services where they've aggregated the data to represent the approximate area covered by a ZIP code. You can find the linked source of the map data at the bottom when you create a new map: 

Datawrapper base maps only include map keys for polygons (areas) and not for points. Therefore, if your dataset includes PO box ZIP codes that are typically represented as single points, you'll find a lot of ZIP codes are left unmatched. A PO box is always located in a ZIP code area so you'll need to find out which ZIP code area these points belong to by searching in a tool like here or finding a crosswalk file to aggregate your data. 

ZIP Code Tabulation Areas (ZCTAs)

If you're creating a map using data from the United States Census Bureau, then we recommend using ZIP Code Tabulation Area (ZCTA) maps instead of the ZIP code maps. If you're plotting a ZIP code level data on a ZCTA map, you can use the Zip code to ZCTA crosswalk file to check which ZIP corresponds to which ZCTA.