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User Agent Lookup API vs Userstack

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

APIUser Agent Lookup APINEW—UserstackNEW—
Uptime · 30d
Uptime · 90d—%—%
Uptime · 30d—%—%
P50 · ms——
P95 · ms——
AuthnoneapiKey
CORSnoyes
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree — limits not publishedFree tier — API key required
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

User Agent Lookup API vs Userstack: common questions

Which is more reliable, User Agent Lookup API or Userstack?

On our scheduled checks, Userstack leads on measured uptime — User Agent Lookup API 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 User Agent Lookup API and Userstack need an API key?

User Agent Lookup API needs no key, while Userstack requires a free API key. If you want to start calling without signup, reach for User Agent Lookup API first.

Can I call User Agent Lookup API and Userstack from the browser?

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

Are User Agent Lookup API and Userstack free for commercial use?

User Agent Lookup API 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.