Frequently Asked Questions


Loadster handles most cookies automatically, but sometimes you need to manually set a cookie yourself. An example of when this might be necessary is if you’re trying to piggyback on existing sessions without actually logging in. […]

How do I parse and validate a JSON response?

When you’re testing a JSON API, don’t just trust the HTTP 2xx responses to mean that everything’s working as expected. Add validation to look at the response bodies coming back and make sure they’re valid JSON and contain the right data. […]

How do I parse and validate an XML response?

When load testing XML web services (like SOAP, XML-RPC, and some RESTful services for example), it’s a good idea to parse the responses to make sure they are well-structured and contain the expected data. […]

How can I play a script that needs to reach a site on a private network?

If your site is on a private network that’s unreachable from the rest of the internet, you’ll need to self-host a Loadster Engine on your own network. […]

How can I ignore socket errors due to an untrusted TLS/SSL certificate?

Loadster normally refuses to talk to sites with untrusted or self-signed certificates, like a normal browser would. If it’s your own site and you want to trust it, you can override this behavior. […]

Can I generate a random string, number, or UUID/GUID?

Sometimes it’s necessary to generate a random string, number, or UUID/GUID in your load test script. You can do this with a function call from an expression. […]

Load Testing

What’s the best way to calculate how many v-users I need for a load test?

Let’s say you know how much total traffic or transactions you need to simulate in a time period. How do you work backwards to estimate how many concurrent v-users it will take to get the job done? […]

Can I override DNS hostnames or use a custom hosts file?

If you’re load testing an alternate environment that’s not available with a normal DNS lookup, read on for how to simulate a custom hosts file. […]

How do I make a test stop after X iterations?

Normally, v-users will continue to run your script over and over as long as there is time remaining in the test. However, you can set an iteration limit to make them stop after a set number of iterations. […]

Can I make Loadster exclude error responses when calculating response times?

Sure! There’s a global setting to do exactly this. […]

Can I get Loadster’s IP addresses for my whitelist?

Some load balancers and firewalls watch for an onslaught of traffic from the same IP, and block it. When running a load test in these environments, you may need to whitelist certain IP addresses. […]

More FAQs

We’ll be adding many more frequently asked questions here. If there’s something you would like to see, please email