Colour Index International is available programmatically as well as through the web interface. The public API serves the catalogue under a stable, versioned URL scheme; downstream applications can resolve a CICN to its full record, search the catalogue, and retrieve fastness data without scraping the HTML surface.
What the API exposes
The API exposes the same Generic Names, Constitution Numbers, fingerprints, commercial product records, and fastness data that the web interface presents — in a structured JSON format suitable for direct consumption. CAS and EINECS / ELINCS cross-references are included on every record. Heritage and retired entries are exposed under their original CICN with a pointer to the modern equivalent where one exists.
Versioning
The current API version is /v1. Versions are introduced when a breaking change is unavoidable; previous versions are supported for at least eighteen months after the next major version ships. Within a version, additive changes (new fields, new endpoints) are routine and do not require a client update.
Authentication and rate limits
API requests authenticate with a per-user bearer token issued from your account settings. The free tier allows a modest rate sufficient for ad-hoc lookup; commercial-licence tiers raise the limit and remove the per-day cap. See the Pricing page for the current limits.
Documentation
The full API reference, OpenAPI specification, and worked examples in Python and JavaScript are available at /v1/docs. The interactive playground lets you try queries against a sandbox dataset without spending live quota.
Commercial use and bulk export
The free API tier is for individual research and prototyping. Production deployments, bulk export, and republication of API responses require a commercial licence — contact licensing@colour-index.com.