Currently, we are using Azure for hosting our web and db. During high load testing of 10k virtual users, we found a tcp connection bottleneck when we reach 3200 users even if we are using multiple servers (and we have adjusted this from two S3 to four S1 instances), and we assume that recaptcha is our bottleneck. We are using the recapthca v2 with test keys. During the tests, we found out that for each user, the recaptcha has 9 HTTP calls, 7 GET and 2 POST.

We are testing a page composed of a form containing a recaptcha control, which we are expecting to have the most hits. We are also expecting as high as 50k users simultaneously using our page on the initial few days. So my question is, is including Google's Recaptcha in a high load test feasible?

  • If this is happening even with "async defer", then i guess that is the way it is. 3200 users seems a bit low though.
    – Janaaaa
    Nov 28, 2017 at 7:32
  • This is a good question, some systems like Google Firebase Auth require the recaptcha object.
    – jmbmage
    Mar 12, 2019 at 14:05

1 Answer 1


You should not be testing reCAPTCHA (or any other internal service), you load test must focus solely on your application only.

Even you find out that reCAPTCHA is a bottleneck I'm afraid you won't be able to do anything with it.

So I would recommend leaving testing reCAPTCHA to Google engineers and turn it off completely. The same you should do for all external images, banners, videos, etc.


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