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The Most Popular Open Source Load Testing Tools

What is Load Testing?

As a developer, you may not notice that the same application that takes some milliseconds to respond in your local development environment, may take seconds in a real production environment unless you test. Testing is the key to many problems in software engineering.

In order to increase the average response time of your applications, you should study how it is impacted by the number of users accessing it concurrently.

This is where load testing tools comes through for you.

This is a test process that involves simulating the user traffic to understand the application’s behaviour while handling multiple requests concurrently. The main metric used in the test is the time taken to give a response to requests made (while taking the concurrency level into consideration).

For instance, you can run a load test with 100 concurrent users to check if the response time of 300 ms is exceeded. To achieve this you need a tool that can generate the required load of requests and still capture the response time accurately.

Before proceeding, you may ask what’s a reasonable response time? The answer depends on the traffic that your website have, but usually an excellent response time do not exceed 100 ms, 300 ms is also a reasonable response time. if your response time exceeds the 1 second, it can be considered slow and if it’s more than 3 seconds, the user experience will surely be impacted.

The Twitter-crashing Selfie & Why You Should Care About Load Testing:

In simple words, an application is competitive because it provides a good user experience. The user experience is not just about UI, features, and usability, it’s also about its capacity to handle the load. Load testing is crucial because:

  • It increases the confidence in the system ability to perform smoothly
  • It allows you to know the application’s capacity
  • It gives you an opportunity to increase the application’s performance.

In 2014, a selfie of celebrities taken by Ellen DeGeneres got just over 2 million retweets in a few hours and this caused Twitter’s website to crash.

The Twitter-crashing selfie is just one case, but the social network app had crashed several times before due to traffic overload. To avoid such scenarios and the financial loss that follows, the company built its own load testing tool, Iago. They opted to internally develop their load tester because they needed a tool that could meet their specific needs.

This is a unique case from a big company capable of developing its own load testing tool.

No worries! You do not have to build your own tool to understand your web application’s performance. We have many capable open-source load testing tools that will get the job done.

In the next section, we discuss some of these tools.

What are the most popular load testing tools?


wrk is a HTTP benchmarking tool that works by combining scalable event notification with multithread design. This tool has the ability to generate test load while running on a single multi-core CPU. It is easily configurable and requires low-overhead due to its concurrency model. The challenge with its that it’s not prepackaged and you, therefore, have to build it before using it.


Vegetta is a HTTP load testing tool written in Golang that can be used both as a library a command-line utility. It is necessitated by the need to drill HTTP services with a constant request rate. This tool is versatile and also very easy to use.


It is a popular load testing tool that is written in Python. To use it, you define the user behavior that you want to apply in the test in regular Python code and that makes it easily scalable. It is an easy-to-use, scriptable, and developer-friendly tool that is lightweight in terms of memory requirements.


This is a modern tool written in Golang and Javascript that provides a clean, approachable scripting API, local and cloud execution, and flexible configuration. All the test logic and configurations are written as JS code. Its biggest advantage is that it provides modules that can be reused.


Apache JMeter is a tool written in pure java which can be used to measure performance and load test static and dynamic web applications. It can be used to simulate a heavy load on a server, group of servers, network, or object to test its strength or to analyze overall performance under different load types. It has an elaborate version history and solid performance history of almost 20 years. One of its biggest advantages is its GUI mode that allows for the creation of tests without writing a single line of code.


This is a benchmark and regression test utility that can be used to perform stress testing. It can do this on a given URL with a defined number of simulated users or read many URLs into memory and stress them simultaneously.

The fact that it can put many URLs under duress simultaneously makes it a very efficient tool for developers.


It is a load test tool that works by replicating real user traffic and directing it to the application so as to analyze its performance. This makes it an effective tool for testing Internet server applications.

This tool is a favorite for many developers because the workload it simulates is very similar to the traffic that users generate.


This Vegeta and jplot inspired tool works by simulating the workload and generating real-time results of the test being undertaken. It has an embedded terminal-based UI where real-time metrics are displayed as the test is being performed.

Its biggest strength is the ability to provide real-time load test results.


This is a HTTP benchmarking command-line line tool for running load tests. It is written in Go and makes use of fasthttp instead of Go’s default http library, because of its lightning-fast performance. This tool is very easy to use and requires minimal resources from your machine.


Just like bombardier, plow is a HTTP benchmarking tool that is also written in Go and makes use of fasthttp instead of http. The difference is that plow gives you real-time record summary statistics, histogram of execution time and calculates percentiles to display on Web UI and terminal. Its real-time computing is inspired by prometheus. Its strengths are its real-time feedback and the low memory it takes to run.

Yandex Tank

It is a benchmarking load testing utility that is suitable for advanced Linux users. It is very effective as part of an automated load testing suite. Its two best features are the capability to store the results online and also the ability to stop the test when the results become obvious. Its shortcoming is that it’s not easy to configure in order to get the most accurate results.


This is a load testing library, command-line tool, advanced echo server, and web UI in go. It allows you to define a set query-per-second load and record latency histograms and other useful stats. This tool is best suited for local testing of the application by developers. However, it does not support scenario-based testing.


This is an automation-friendly load testing tool that relies on JMeter, Gatling,, and Selenium WebDriver as its underlying tools. It works as an abstraction layer on top of other load testing tools. This tool allows for the use of a simple YAML-based configuration format with DSL that is executed through the command line.


It’s a modern and flexible load testing framework for Pull and Push scenarios, designed to test any system regardless of the protocol (HTTP/WebSockets/AMQP etc) or a semantic model (Pull/Push). It is a favorite for many developers because it’s lightweight and can test any system from database to web server or message broker.


A webserver performance measurement tool that provides a flexible facility for generating various HTTP workloads. The focus of httperf is not on implementing one particular benchmark but on providing a robust, high-performance tool that facilitates the construction of both micro-and macro-level benchmarks. The three distinguishing characteristics of httperf are its robustness, which includes the ability to generate and sustain server overload, support for the HTTP/1.1 and SSL protocols, and its extensibility to new workload generators and performance measurements.

Implement reliable load testing with WildCard!

Whether you are building the next Twitter or the next idea that will change your industry, load testing is important for you. The good news is that you can add it to your CI/CD pipelines. When you have a major release involving a change in the database schema, a new architecture, new technology or anything that may impact the workload, automated load testing will be useful as it’s done and evaluated continuously.

You can create an entire CI/CD pipeline with minimal coding and integrate your load testing tool in minutes. Try it here for free.

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Muhammad Ali


I am a growth Marketer
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