What a Wonderful Morning! We don’t have a hard cap, however there is a restriction to the length of a URL, so I suggest restricting it to 500 characters or less. The maximum number of zip code boundaries that will be returned from a query is 200. In addition, many of our customers take advantage of the parameter combine=true, which causes us to display a combined boundary if the zip codes are close together. while showing more than a hundred code areas at once. For those who volunteer the supplementary drift boss

Good Morning, We actually don’t have a max but there is a limit to how large a URL so I recommend keeping it under 500 or so. You can query a few hundred( example 200) and it will return 200 zip code boundaries… the max. Also, if the zip codes are clustered together you can add the parameter combine=true to show a combined boundary for better visualization, many of our clients use that feature. when displaying over 100 zip codes at once. if you provide the optional
header ( “Accept” : “application/topojson”) , the response size is reduced significantly but the response format will be in TopoJson instead of GeoJson.