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arcsecond.io vs Open Notify

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

APIarcsecond.ioNEW—Open NotifyDYING—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
Authnonenone
CORSyesyes
HTTPSyesno
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedn/a
Free tierFree — limits not publishedUnlimited (volunteer-run)
Rate limitUnpublishedPlease be gentle
In directory since2026-07-052026-05-02
operationalpartialdownno data

arcsecond.io vs Open Notify: common questions

Which is more reliable, arcsecond.io or Open Notify?

On our scheduled checks, Open Notify leads on measured uptime — arcsecond.io at —% versus Open Notify 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 arcsecond.io and Open Notify need an API key?

Neither needs a paid key — arcsecond.io is callable with no signup, and Open Notify is callable with no signup. Both are quick to prototype with; rate limits still apply.

Can I call arcsecond.io and Open Notify from the browser?

Only arcsecond.io is browser-friendly — it returns CORS headers over HTTPS. Open Notify needs a server-side call or proxy, so factor that into which one fits a front-end project.

Are arcsecond.io and Open Notify free for commercial use?

arcsecond.io has unclear commercial terms, and Open Notify 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.