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The best load testing tools for developers

Photo of David Mytton David Mytton

Last updated: 2021-10-22

From 2009-2018 David was CEO at Server Density, a SaaS server monitoring startup. He has been a developer for 15+ years and is now co-founder of Console.

✦ Disclosure: All reviews are editorially independent and partners must meet our selection criteria. Where indicated, we work with some partners to provide extras to our audience, but do not accept payment for reviews.


Load testing tools help understand whether your infrastructure can handle a large spike of traffic and how fast pages load. The best load testing tools provide scriptable test plans, protocol- and browser-level test execution, and for this review must also have a developer focus.

We tested 11 load testing tools using our independent selection criteria and the requirements described below. The best 6 load testing tools for developers and engineers in 2021 are:

  1. Flood
  2. k6
  3. Locus
  4. Loadster
  5. Gatling
  6. Apache JMeter

In this article, we explain why. We assessed the key features all load testing tools should have from the perspective of an experienced developer.

What is the difference between load testing and browser testing?

Load testing is focused on sending lots of requests to simulate a traffic spike or a sudden influx of users. It examines the infrastructure with a focus on errors and measuring response time. This can be achieved through protocol-level requests to HTTP, WebSockets or API endpoints, but can also be implemented using browser simulations.

Testing with a real browser is important to ensure that the page resources load and the pager renders quickly. Protocol-level testing does not load all the extra resources a page may reference, such as third party scripts or images. Browser-level testing load everything, which means the infrastructure gets fully tested.

Browser testing is focused on browser compatibility to ensure that the web page renders correctly across different versions and platforms. The best browser testing tools allow tests on many different browsers, including older versions and mobile browsers. The browser version or platform do not matter for load testing.