9 Best Load Testing Tools

Ensure a seamless user experience is key to a successful modern application.

Developers, DevOps and SREs, need to ensure that applications can withstand stress and influx in the number of concurrent users. However, this cannot be assured unless the application's performance is tested in a simulated scenario.

Load testing, according to Wikipedia refers to "the practice of modelling the expected usage of a software program by simulating multiple users accessing the program concurrently." Load testing helps to understand the number of requests or concurrent users your application can handle optimally by replicating a real-life scenario.

This article reviews some of the best paid and open-source tools to help you perform load tests for your web applications, API, URLs, and servers.

Gatling

Gatling is an enterprise load testing tool that helps you detect errors and performance issues early in your application development phase. It is designed to enable continuous load testing for your applications, and it integrates with your DevOps and CI/CD pipeline for repeatable tests. Gatling offers a Cloud SaaS and Self hosted solution with the Cloud offer starting from EURO69 per month.

k6

Recently acquired by Grafana Labs, k6 is an open-source load testing tool offered as a SaaS and self-hosted product. With an impressive 13k+ stars on GitHub, k6 offers easy and powerful scripting with JavaScript. It allows you to create and automate load tests similar to real-world scenarios and can be used by developers, DevOps and SREs, software testers, and QAs. k6 integrates with popular tools like Grafana, GraphQl, and Datadog and CI/CD tools like CircleCI and GitLab.

Apache JMeter

Apache JMeter is a matured and widely used open-source load and performance testing tool written in Java. In addition to performing load testing for static and dynamic web applications, JMeter can be used for load testing different servers, databases, middlewares, and protocols. It offers a full-featured IDE for testing, building, and debugging applications and a CLI mode with support for Windows, Linux, and macOSX. It integrates with CI tools like Jenkins, Gradle, and Maven. It also allows you to correlate and extract the test results in HTML, JSON or XML formats.

Loader

Loader presents itself as a "free load testing service." It allows you to stress test

your web apps and Apis with thousands of concurrent connections and monitor the test in real-time through its graphical web interface. Loader is also offered as an API that integrates into your CI/CD pipeline to load test your applications continuously. Loader offers a free plan with a single host, one-minute tests and 10,000 clients per test. Its pro version starts from $99.95 per month with unlimited targets, 10 minutes tests and up to 100,000 clients per test.

Flood

Flood is a load testing platform that simulates connections to execute distributed performance tests for applications at scale. It can be deployed on a single, hybrid cloud or on-premise infrastructure with a simple GUI that makes the execution of tests easy. It allows you to write your test scripts from the Flood UI or upload a script from load testing tools like JMeter, Gatling or Selenium. You also get to monitor your test in real-time, and the results are represented in intuitive UI for further performance analysis.

Flood offers a free monthly 500 virtual user hours VUH credit with the price per VUH starting from $0.045.

RedLine13

RedLine13 is a continuous load testing tool that allows you to stress test URLs, web apps and API. It will enable you to run your existing JMeter, Selenium, Gatling, and WebDriver test at scale while saving cost by leveraging AWS cloud. It integrates with your existing workflow to enable repeatable and continuous load testing. It offers a free plan with unlimited tests and 10vCPUs for single users, and its paid plan for 50 vCPUs starts from $75 per month.

LoadNinja

LoadNinja provides a platform for testing applications' performance and user experience across tens of thousands of simulated browsers. It offers a web UI that allows you to create, run, record and replay load tests to diagnose web apps and APIs performance. It also presents data and metrics of load tests to analyze performance data like step times, resources processed by the browser, and navigation timing. LoadNInja pricing starts from $289 per month or $1,239 per annum.

nGrinder

nGrinder is an open-source enterprise-level performance testing platform that allows you to create a script, run, and monitor stress tests for web applications. nGrinder test scripts are written in Python, and it provides an integrated environment that enables the easy configuration and execution of load tests. It provides a web-based interface for project management, monitoring, result management and report management and also allows you to run multiple tests concurrently.

Locust

Boasting of a record 21.4k running users, locust is an open-source load testing tool that allows you to create test scenarios in Python. It provides a test template that makes it easy to create test scenarios in Python and load test your applications with millions of simultaneous users. It supports running on distributed machines, which aids its ability to simulate millions of concurrent users.