Guides
for everything Geocodio
Guides
OCD IDs
Guides
for everything Geocodio
OCD IDs
/OCD identifiers (Open Civic Data Division IDs) are unique identifiers for political districts established by Open Civic Data.
For example, the OCD-ID for Virginia's 8th Congressional District is ocd-division/country:us/state:va/cd:8.
When you use Geocodio to process addresses and append electoral districts, we include OCD IDs when available.
Many civic tech tools and government APIs use these same identifiers, which makes it easy to match district data between sources.
UK OCD IDs
UK districts are referenced by two different identifier systems: GSS codes and OCD IDs. Geocodio includes both where available. See the UK identifiers section below.
All districts and OCD-IDs provided by Geocodio
Below you'll find lists of all political districts returned by Geocodio and their corresponding OCD-IDs.
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UK
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USA
Canada
UK Identifiers: GSS Codes and OCD IDs
GSS Codes
GSS (Government Statistical Service) codes are the authoritative UK government identifiers, published and maintained by the Office for National Statistics. Every UK district returned by Geocodio includes a GSS code. If you need a stable, universally recognized identifier for a UK district, use the GSS code.
GSS codes follow a consistent format (e.g. E14001172 for a Westminster constituency in England, W05001234 for a Welsh ward). The first letter indicates the nation: E for England, S for Scotland, W for Wales, N for Northern Ireland.
OCD IDs
OCD IDs come from the Open Civic Data project, the same identifier system Geocodio uses for US Congressional districts. They are human-readable string identifiers (e.g. ocd-division/country:gb/part:eng/region:uki/ed:cities_of_london_and_westminster).
OCD IDs are useful if you already work with Open Civic Data in other contexts. They are not a canonical UK dataset, so coverage varies by district type. See the OCD-IDs guide for more:
| District Type | OCD ID Coverage |
|---|---|
| Westminster constituencies | 650 of 650 (full) |
| NI Assembly constituencies | 18 of 18 (full) |
| Scottish Parliament constituencies | 7 of 73 (partial) |
| Scottish Parliament regions | 0 of 8 (derived only) |
| Senedd constituencies | 0 of 16 (derived only) |
| Wards and County Electoral Divisions | Derived only |
ocd_id is always populated — the canonical ID where one exists, otherwise a derived OCD-format ID from the GSS code/name (uk-westminster or uk-devolved). For uk-local, rows always include a derived ocd_id field (e.g., …/ward:e05014959). Open Civic Data does not maintain any identifiers for UK local government.
An ocd_id is returned for all 16 Senedd constituencies, but it's a Geocodio-generated OCD-format identifier built from the GSS code and constituency name, not a canonical Open Civic Data registry entry. Use gss_code as the authoritative identifier for Senedd.
Effective 2026-05-07, the Senedd moved from 40 constituencies + 5 regions to 16 reformed constituencies, no region row. Identifiers use the W09 GSS series (W09000048–W09000063) with Welsh-language names. Boundaries published via DataMap.Wales; API source value is Welsh Government.