Want to test how your server performs under load? If you’re in the process of optimizing a server, or have just installed a caching solution, it’s good to see the effect your changes have had.

Blitz is a configurable service that will pound your site with page requests, allowing you to specify the concurrency, timeout, and duration of the onslaught. As it goes about this, it builds statistics and plots them along timelines. You can watch response times, errors and timeouts as it slowly ramps up the number of concurrent users until it reaches the maximum. At the end, it even projects how many hits per day your setup can handle at that rate.

The service has a generous free tier, though they offer paid upgrades for higher concurrency and duration. The free tier offers 250 concurrent users over a one minute rush. (Though if you sign up with this invite link, they will add additional concurrencies to your account.)

I found Blitz very useful when I was trying to squeeze faster response times out of my WordPress setup, tweaking my caching system options and adjusting Nginx and PHP configurations. Since they use the connections at their datacenter, you get more real-world results than if you simply ran Apache Bench locally on the server, or from your residential internet connection. Both tools have their uses, of course, and Blitz is a good one to have in your arsenal.