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ClinicalTrials.gov vs openFDA API

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

APIClinicalTrials.govHEALTHY78openFDA APIHEALTHY93
Uptime · 30d
Uptime · 90d100%100%
Uptime · 30d100%100%
P50 · ms138305
P95 · ms35331868
Authnonenone
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

ClinicalTrials.gov vs openFDA API: common questions

Which is more reliable, ClinicalTrials.gov or openFDA API?

Both are neck-and-neck — ClinicalTrials.gov and openFDA API each measure 100% uptime over 90 days on our probe schedule. Reliability here is verified from our own scheduled checks; use the 30-day bars above to see which has been steadier lately.

Which is faster, ClinicalTrials.gov or openFDA API?

ClinicalTrials.gov has the lower median latency in our checks — ClinicalTrials.gov responds in 138 ms versus openFDA API at 305 ms (P50). Tail latency (P95) is in the table above; for most workloads the median is the number that shapes how the API feels.

Do ClinicalTrials.gov and openFDA API need an API key?

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

Can I call ClinicalTrials.gov and openFDA API from the browser?

Only ClinicalTrials.gov is browser-friendly — it returns CORS headers over HTTPS. openFDA API needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are ClinicalTrials.gov and openFDA API free for commercial use?

ClinicalTrials.gov has unclear commercial terms, and openFDA API 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.