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OpenHolidays API vs PostStack

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

APIOpenHolidays APIHEALTHY94PostStackHEALTHY87
Uptime · 30d
Uptime · 90d100%100%
Uptime · 30d100%100%
P50 · ms5331066
P95 · ms39201890
AuthnoneapiKey
CORSyesno
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree tier — key may be required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

OpenHolidays API vs PostStack: common questions

Which is more reliable, OpenHolidays API or PostStack?

Both are neck-and-neck — OpenHolidays API and PostStack 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, OpenHolidays API or PostStack?

OpenHolidays API has the lower median latency in our checks — OpenHolidays API responds in 533 ms versus PostStack at 1066 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 OpenHolidays API and PostStack need an API key?

OpenHolidays API needs no key, while PostStack requires a free API key. If you want to start calling without signup, reach for OpenHolidays API first.

Can I call OpenHolidays API and PostStack from the browser?

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

Are OpenHolidays API and PostStack free for commercial use?

OpenHolidays API has unclear commercial terms, and PostStack 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.