Load Testing Tools

As websites, web applications, APIs and services become more and more critical, it's import to design and build applications so that they scale well for a large number of requests. To actually test and verify the behavior of services under load, testers and developers can perform load and stress tests. For web applications a load test would usually involve defining, writing and running test scenarios.

A test scenario could be a script that simulates the behavior of a typical user across multiple pages of a website or web application. Once you defined your test scenarios, you can execute it by simulating many concurrent virtual users and monitor how your application behaves. Likewise for APIs and other services, the idea is to generate requests that are as realistic and similar to the possible load of your production environment, so you can optimize and scale your application and services based on accurate and realistic data.

Load Testing Tools 8 Tools

There are various tools that you can use to build, conduct and analyze load and stress tests for web applications and other services. Most tools require that you build test scenarios, usually scenarios a typical user would perform on a website, and then simulate many virtual users simultaneously.

Open Source


JMeter is an open source Java-based load and performance testing tool. Besides testing web applications and services, you can also load test other services such as LDAP, mail servers or databases.

Open Source


Tsung is an open source multi-protocol distributed load testing tool. The purpose of Tsung is to simulate users in order to test the scalability and performance of services, such as HTTP servers and other services.

Open Source


This is a tool for benchmarking your HTTP server. It is designed to give you an impression of how your current Apache (or other web server) installation performs. This especially shows you how many requests per second your Apache installation is capable of serving and can be useful to benchmark web applications and APIs as well.

Open Source


Locust is a scalable and distributed load testing tool for web applications, websites and web-based services. Locust comes with a web-based user interface and allows you to write test scenarios in Python.



WAPT is a load and stress testing tool that allows you to build, generate and monitor load tests via a graphical user interface. WAPT comes in two editions and doesn't limit the number of virtual users you can use like most other commercial tools do.


Webserver Stress Tool

The Webserver Stress Tool is an advanced load testing tool that comes with a graphical user interface to run and analyze your load tests. This tool can generate a number of different tests to verify your web applications and services.



LoadUI is a cross-platform load and stress testing tool. LoadUI is available as both open source and commercial editions. Its UI allows you to create, configure and redistribute your load tests interactively and in real-time.



Loadster it a load and stress testing tool specifically designed for high-performance web applications. It comes in two parts: a tool to build and design your test scenarios, and an engine that you can use to actually run and distribute your load tests.

Load Testing Cloud Services

In addition to the above mentioned load testing tools, the following services make it easy to start large-scale load tests without having to build your own infrastructure. This is especially useful if you only have to conduct such tests from time to time, e.g. at specific points in your development efforts.

Service Type Description Pricing
BlazeMeter Web & APIs JMeter-compatible load testing service Starting @ $199/month
LoadStorm Web & APIs SaaS cloud testing service Starting @ $40/month
Load Impact Web & APIs Websuite load testing service Starting @ $60
Loader.io Web & APIs Free cloud testing service by Sendgrind Free

Load Testing Books 4 Books

The following books provide a good starting point and overview to learn more about load testing websites, web applications, APIs and more. Load testing is usually just one aspect of optimizing web-based applications so most of the listed books cover load testing as part of a larger testing strategy.

The Art of Application Performance Testing: Help for Programmers and Quality Assurance

Ian Molyneaux, 160 Pages, O'Reilly Media

Written by a consultant with 30 years of experience in the IT industry and over 12 years experience with performance testing, this easy-to-read book is illustrated with real-world examples and packed with practical advice. The Art of Application Performance Testing thoroughly explains the pitfalls of an inadequate testing strategy and offers you a robust, structured approach for ensuring that your applications perform well and scale effectively when the need arises.

Testing Applications on the Web: Test Planning for Internet-Based Systems

Hung Q. Nguyen, 400 Pages, Wiley

Written by a true authority in the field, Hung Q. Nguyen's Testing Applications on the Web is a nicely comprehensive guide to virtually every conceivable aspect of software testing. It's filled with must-have background information for any test engineer or manager who's testing thin-client systems.

Performance Testing Guidance for Web Applications

Microsoft Corporation, 288 Pages, Microsoft Press

Performance Testing Guidance for Web Applications provides an end-to-end approach for implementing performance testing. Whether you are new to performance testing or looking for ways to improve your current performance-testing approach, you will gain insights that you can tailor to your specific scenarios.

High Performance Web Sites: Essential Knowledge for Front-End Engineers

Steve Souders, 170 Pages, O'Reilly Media

Author Steve Souders, in his job as Chief Performance Yahoo!, collected these best practices while optimizing some of the most-visited pages on the Web. Even sites that had already been highly optimized, such as Yahoo! Search and the Yahoo! Front Page, were able to benefit from these surprisingly simple performance guidelines. If you're building pages for high traffic destinations and want to optimize the experience of users visiting your site, this book is indispensable.

Additional Load Testing Resources

In addition to the above mentioned books, there's a huge number of online resources to help you get started with load testing and testing the performance of web applications and web sites. We researched the best articles and online resources and please see the list of links below.

Load Testing in 10 Steps

"Most of the software companies are running Load Testing on their products. Load testing is one of the most important testing types today. In this article, I'm not going to talk about Load Testing tools or advanced testing techniques, but rather, I would like to talk about 10 basic steps that are the foundations for creating a good, precise and powerful Load Test suite."

3 Key Load Testing Tips

"So what?! I still say you should test against production. And so would some others in our industry that have much more experience than I. For example, Dan Bartow taught a couple of sessions in April at STPCon in San Mateo. He mentioned several times that hammering the real production servers is the only way."

Real-World Load Testing Tips to Avoid Bottlenecks

"Load testing should be part and parcel of every Web development effort, and it should be performed early in the process. However, if you think you can load test using your development environment, you're going to have some surprises when you go live."

Best Practices for Successful Load Testing

"Load testing requires a good deal of planning and forethought. Many items need to be taken into consideration to maximize effectiveness. To that end, the testing process should occur over the course of several weeks to allow for careful planning, test execution and a thorough examination of testing results."

A Beginner's Guide to Application Load Testing (presentation)

"Now you have finished your site and someone asked you the question: How many users can we serve before we need more power and muscle on our server environment? Good question! And if you don't know how to find that out, how to measure it, and find the bottle necks, come to this session. You'll find out how to get started and learn more about tools for [web] application load testing and how to use them."

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Load Testing

Load testing is the process of putting demand on a system or device and measuring its response. Load testing is performed to determine a system's behavior under both normal and anticipated peak load conditions. It helps to identify the maximum operating capacity of an application as well as any bottlenecks and determine which element is causing degradation.

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