Userstack vs VATlayer
Same instrument, two spec sheets — measured, not claimed.
Userstack vs VATlayer: common questions
Which is more reliable, Userstack or VATlayer?
On our scheduled checks, VATlayer leads on measured uptime — Userstack at 99.02% versus VATlayer 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, Userstack or VATlayer?
Userstack has the lower median latency in our checks — Userstack responds in 443 ms versus VATlayer at 473 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 Userstack and VATlayer need an API key?
Both ask you to authenticate — Userstack uses an API key and VATlayer 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 Userstack and VATlayer from the browser?
Only Userstack is browser-friendly — it returns CORS headers over HTTPS. VATlayer needs a server-side call or proxy, so factor that into which one fits a front-end project.
Are Userstack and VATlayer free for commercial use?
Userstack has unclear commercial terms, and VATlayer 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.