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ClinicalTrials.gov vs openFDA

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

APIClinicalTrials.govHEALTHY77openFDAHEALTHY78
Uptime · 30d
Uptime · 90d99.02%94.1%
Uptime · 30d100%93.3%
P50 · ms2431187
P95 · ms5744661
Authnonenone
CORSyesyes
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: common questions

Which is more reliable, ClinicalTrials.gov or openFDA?

On our scheduled checks, ClinicalTrials.gov leads on measured uptime — ClinicalTrials.gov at 99.02% versus openFDA at 94.1% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Which is faster, ClinicalTrials.gov or openFDA?

ClinicalTrials.gov has the lower median latency in our checks — ClinicalTrials.gov responds in 243 ms versus openFDA at 1187 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 need an API key?

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

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

Yes — both ClinicalTrials.gov and openFDA 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 openFDA free for commercial use?

ClinicalTrials.gov has unclear commercial terms, and openFDA 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.