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ClickSend REST API v3 vs SLF

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

APIClickSend REST API v3NEW—SLFNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeynone
CORSyesyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — API key requiredFree — static file, no key
Rate limit6000 req/window · 5999 remaining · resets 1Unpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

ClickSend REST API v3 vs SLF: common questions

Which is more reliable, ClickSend REST API v3 or SLF?

On our scheduled checks, SLF leads on measured uptime — ClickSend REST API v3 at —% versus SLF 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 ClickSend REST API v3 and SLF need an API key?

SLF needs no key, while ClickSend REST API v3 requires a free API key. If you want to start calling without signup, reach for SLF first.

Can I call ClickSend REST API v3 and SLF from the browser?

Yes — both ClickSend REST API v3 and SLF 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 ClickSend REST API v3 and SLF free for commercial use?

ClickSend REST API v3 has unclear commercial terms, and SLF 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.