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ClinicalTrials.gov vs OpenF1

Same instrument, two spec sheets — measured, not claimed.

APIClinicalTrials.govNEW—OpenF1NEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree & open (historical); real-time may require a free account
Rate limitUnpublishedRetry-After: 60s
In directory since2026-07-052026-07-05
operationalpartialdownno data

ClinicalTrials.gov vs OpenF1: common questions

Which is more reliable, ClinicalTrials.gov or OpenF1?

On our scheduled checks, OpenF1 leads on measured uptime — ClinicalTrials.gov at —% versus OpenF1 at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Do ClinicalTrials.gov and OpenF1 need an API key?

Neither needs a paid key — ClinicalTrials.gov is callable with no signup, and OpenF1 is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call ClinicalTrials.gov and OpenF1 from the browser?

Yes — both ClinicalTrials.gov and OpenF1 send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.

Are ClinicalTrials.gov and OpenF1 free for commercial use?

ClinicalTrials.gov has unclear commercial terms, and OpenF1 has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.