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BulkSMS JSON REST API vs caldays

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

APIBulkSMS JSON REST APINEW—caldaysNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeynone
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

BulkSMS JSON REST API vs caldays: common questions

Which is more reliable, BulkSMS JSON REST API or caldays?

On our scheduled checks, caldays leads on measured uptime — BulkSMS JSON REST API at —% versus caldays 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 BulkSMS JSON REST API and caldays need an API key?

caldays needs no key, while BulkSMS JSON REST API requires a free API key. If you want to start calling without signup, reach for caldays first.

Can I call BulkSMS JSON REST API and caldays from the browser?

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

Are BulkSMS JSON REST API and caldays free for commercial use?

BulkSMS JSON REST API has unclear commercial terms, and caldays 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.