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serpstack vs Userstack

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

APIserpstackNEW—UserstackNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthapiKeyapiKey
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — key may be requiredFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

serpstack vs Userstack: common questions

Which is more reliable, serpstack or Userstack?

On our scheduled checks, Userstack leads on measured uptime — serpstack at —% versus Userstack 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 serpstack and Userstack need an API key?

Both ask you to authenticate — serpstack uses an API key and Userstack uses an API key. Each key is free to obtain; the Auth and Card-required rows above spell out the signup terms.

Can I call serpstack and Userstack from the browser?

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

Are serpstack and Userstack free for commercial use?

serpstack has unclear commercial terms, and Userstack 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.