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ImprovMX API vs The Calendar

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

APIImprovMX APIUNMONITORED—The CalendarNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeynone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified (US federal list per 5 U.S.C. § 6103)
Free tierFree tier — API key requiredFree, no auth (per site)
Rate limitUnpublishedNone stated (site advertises no rate limit)
In directory since2026-07-052026-07-05
operationalpartialdownno data

ImprovMX API vs The Calendar: common questions

Which is more reliable, ImprovMX API or The Calendar?

Only The Calendar is on our probe schedule so far (—% uptime over 90 days). The other is catalogued but not yet live-checked, so we can't compare measured reliability head-to-head — check the uncovered API's own status page for now.

Do ImprovMX API and The Calendar need an API key?

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

Can I call ImprovMX API and The Calendar from the browser?

Yes — both ImprovMX API and The Calendar 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 ImprovMX API and The Calendar free for commercial use?

ImprovMX API has unclear commercial terms, and The Calendar 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.