CARTOS – ONC’s Terminology Service 

Welcome to Cartos, on HealthIT.gov. Cartos is a public, FHIRยฎ-enabled terminology service provided by the Office of the National Coordinator for Health IT (ONC). It helps implementers find, understand, and use terminology content connected to the ONC Health IT Certification Program, the Standards Version Advancement Process (SVAP), and supported implementation guides.

Cartos User Guide

Overview

Today, implementers often need to gather terminology information from several different sources.  Code systems and value sets may be found in HL7ยฎ repositories, US Health and Human Services websites or terminology repositories, and implementation guides. The same code system or value set may exist in multiple places, with different versions, leaving the implementer to speculate which is the right one. This can take extra time and make it difficult for users to find the content they need.

Cartos streamlines and simplifies this process by bringing regulatory context, implementation guide references, terminology metadata, and terminology content together in one coordinated location. Users can access information through browser-based search, a standards-based FHIR R4 API, or downloadable terminology collections. This helps users find what they need faster, confirm they are using the right terminology version, reduce duplicate research, and support more consistent implementation across health IT products and public health use cases.

Cartos does not provide API access to return large clinical code systems that have well established distribution mechanisms such as NLM, Regenstrief Institute, CDC, CMS, FDA, or other standards organizations. Instead, it helps users locate and use terminology content in a way that is connected to ONC regulations, the ONC Health IT Certification Program, SVAP, and implementation guides.

About Cartos Terminology Service

Cartos provides centralized access to terminology resources used to support standards-based health data exchange. The service includes two primary access methods:

Cartos FHIR API: A read-only, FHIR R4-based API that allows developers and integration teams to retrieve, search, expand, look up, and validate terminology content programmatically.

Cartos Terminology Browser: A web-based interface that allows users to search and browse terminology content without installing software or creating an account.

Cartos on HealthIT.gov Public Access

Cartos is intended to support health IT implementation, certification readiness, interoperability testing, public health reporting, and ongoing terminology maintenance activities. Users may search the terminology browser, connect to the FHIR API, or download available terminology collections from HealthIT.gov.

The Cartos API is a shared public resource. Rate limits and fair-use expectations help keep the service available and responsive for all users.

Terms of Use

Using Cartos , including the terminology browser, FHIR API, and terminology collection downloads, means you agree to use the service responsibly and follow all applicable terminology licensing and use requirements.

The Cartos API is intended for health IT integration, implementation, validation, testing, and research. Do not use Cartos to bulk-harvest content beyond what your implementation reasonably requires.

Users are responsible for following the licensing, attribution, redistribution, and use requirements for each code system or terminology steward represented in Cartos. If you download or redistribute Cartos content, you must follow the applicable licensing terms for each code system or terminology resource included in that content.

Some terminology content may be limited, unavailable, or provided only as metadata because of licensing, proprietary content restrictions, steward distribution requirements, or technical constraints.

Misuse of Cartos, including attempts to bypass rate limits, overload the service, scrape excessive content, or use automated workarounds, may result in rate limiting, blocking, or suspension of access.

Cartos does not replace official content stewards, source terminology licensing requirements, implementation guides, regulations, or organizational compliance review.

Contact the Team

For technical support questions related to server access, system latency, performance degradation, rate-limit increase requests, or other technical issues, contact the ONC Cartos team through the ONC Cartos Support Portal.

For questions related to terminology assets, including code systems, value sets, or collections, contact the ONC Cartos team.

When submitting a request, please include enough detail for the team to review, assess, and route the request appropriately. Helpful information may include:

  • Value set or code system name
  • Canonical URL or identifier
  • Version
  • API request or endpoint used
  • Error message or response code
  • Related regulation, SVAP, or implementation guide
  • Description of the issue or requested change
  • Requested rate-limit change, if applicable