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serpstack vs User Agent Lookup API

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

APIserpstackHEALTHY93User Agent Lookup APIHEALTHY96
Uptime · 30d
Uptime · 90d99.02%100%
Uptime · 30d98.3%100%
P50 · ms492426
P95 · ms1442764
AuthapiKeynone
CORSnono
HTTPSyesyes
Card requirednono
Commercial useunclearunclear
Data licenseUnverifiedUnverified
Free tierFree tier — key may be requiredFree — limits not published
Rate limitUnpublishedUnpublished
In directory since2026-07-052026-07-05
operationalpartialdownno data

serpstack vs User Agent Lookup API: common questions

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

On our scheduled checks, User Agent Lookup API leads on measured uptime — serpstack at 99.02% versus User Agent Lookup API at 100% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.

Which is faster, serpstack or User Agent Lookup API?

User Agent Lookup API has the lower median latency in our checks — serpstack responds in 492 ms versus User Agent Lookup API at 426 ms (P50). Tail latency (P95) is in the table above; for most workloads the median is the number that shapes how the API feels.

Do serpstack and User Agent Lookup API need an API key?

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

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

Neither sends browser-friendly CORS headers reliably, so call serpstack and User Agent Lookup API from a server or proxy rather than client-side. The CORS and HTTPS rows above show exactly what we detected for each.

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

serpstack has unclear commercial terms, and User Agent Lookup API 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.