City, Nantes Open Data vs Colorado Information Marketplace

Nantes Métropole's open-data portal runs OpenDataSoft; the stored record's `API Key` requirement is stale — a live keyless GET against the v2.1 Explore API (`data.nantesmetropole.fr/api/explore/v2.1/catalog/datasets`) returned full JSON catalogue metadata with a wildcard `Access-Control-Allow-Origin` header, and dataset exports in GeoJSON and CSV worked the same way with no key. An API key is only required for OpenDataSoft's write/administration endpoints, not for reading the catalogue's 590+ datasets.

The Colorado Information Marketplace is the state's open-data portal, built on the Socrata platform and covering budget, transportation, public-safety, and demographic datasets from Colorado agencies. Every dataset is queryable through Socrata's SODA REST API without an account, with an optional free app token only needed to raise the anonymous rate limit. Results are returned as JSON by default, with CSV and XML also available per dataset.