ClinicalTrials.gov

ClinicalTrials.gov Classic API

RETIRED. The Classic API was withdrawn in June 2024 and its endpoints now return HTTP 404 (probed 2026-09-06: /api/query/full_studies and /api/info/data_vrs both 404). It is retained here only so consumers of the legacy surface can find the migration path. Originally the legacy ClinicalTrials.gov interface that preceded the Data API v2 and exposes full-study, brief-study, and field-values endpoints with XML, JSON, and CSV responses. It is being deprecated in favor of the v2 REST API and remains online for backward compatibility while consumers migrate.

GitHub

Documentation

📖
Documentation
https://clinicaltrials.gov/data-api/api

Other Resources

🔗
Deprecation
https://clinicaltrials.gov/data-api/about-api/api-migration
🔗
Lifecycle
https://raw.githubusercontent.com/api-evangelist/clinical-trials-gov/refs/heads/main/lifecycle/clinical-trials-gov-lifecycle.yml
🔗
APIsJSON
https://raw.githubusercontent.com/api-evangelist/clinical-trials-gov/refs/heads/main/apis.yml

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API entry from apis.yml

apis.yml Raw ↑ 
aid: clinical-trials-gov:classic-api
name: ClinicalTrials.gov Classic API
tags:
- Clinical Trials
- Legacy
- REST
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
baseURL: https://clinicaltrials.gov/api
humanURL: https://clinicaltrials.gov/data-api/api
properties:
- url: https://clinicaltrials.gov/data-api/api
  type: Documentation
- url: https://clinicaltrials.gov/data-api/about-api/api-migration
  type: Deprecation
- url: lifecycle/clinical-trials-gov-lifecycle.yml
  type: Lifecycle
description: 'RETIRED. The Classic API was withdrawn in June 2024 and its endpoints now return HTTP 404
  (probed 2026-09-06: /api/query/full_studies and /api/info/data_vrs both 404). It is retained here only
  so consumers of the legacy surface can find the migration path. Originally the legacy ClinicalTrials.gov
  interface that preceded the Data API v2 and exposes full-study, brief-study, and field-values endpoints
  with XML, JSON, and CSV responses. It is being deprecated in favor of the v2 REST API and remains online
  for backward compatibility while consumers migrate.'