On the planet of software program growth, testing is significant. Irrespective of how effectively you code or how thorough your preliminary testing course of could also be, there’s all the time an opportunity that one thing will slip via the cracks.
That’s why load testing is so necessary. And whereas loads of industrial instruments on the market may help you with this course of, open-source load testing software program can be obtainable
On this information, you’ll study:
- The significance of load testing
- Prime open-source and FREE efficiency load testing instruments in your load and stress testing efficiency engineering efforts
- Some key options of every load testing software program
Why is it necessary to include load testing early and recurrently in software program testing practices?
Load testing is a particular sub-family of a efficiency check that features many concurrent customers working the identical program on the similar time. That is executed to see whether or not a system infrastructure can deal with the load with out compromising performance or simply with acceptable efficiency degradation.
Load testing is used to assist decide if:
- The response time returned from crucial actions in your software is suitable in comparison with specification, person necessities, or KPI.
- Are your key enterprise performance behaving correctly beneath heavy load
- Is your infrastructure designed to scale beneath stress checks
Entrance-end efficiency testing measures how briskly your web site hundreds and shows content material for customers. In distinction, back-end efficiency testing entails sending a number of requests to your servers to see if they will deal with simultaneous requests. Most efficiency testing instruments solely check API endpoints, however instruments like xk6-browser transcend that by testing browser efficiency as effectively.
Efficiency testing instruments, basically, are crucial to buyer satisfaction. They are going to transfer on to your competitor in case your software efficiency does not meet your buyer’s expectations or all service degree agreements.
Is load testing thought-about non-functional or purposeful testing, and why?
Load testing is usually thought-about a non-functional sort of testing as a result of it focuses on testing efficiency, reliability, and useful resource utilization traits slightly than specific features or person tales.
Nevertheless, poor efficiency immediately impacts person expertise and may render an software successfully unusable, so organizations should not take into account efficiency as purely non-functional. There may be overlap with purposeful testing, particularly for catching points like race situations or useful resource leaks that solely manifest beneath load.
The very best strategy is to include load testing alongside purposeful testing in an built-in method to construct an general high quality product. Devoted load testing remains to be wanted to emphasize the system and discover limits.
Begin Load Testing Early
Incorporating load testing early and recurrently in software program testing practices is essential for a number of causes.
Firstly, load testing permits software program builders to judge how a system features beneath high-stress situations, similar to when a number of customers are concurrently accessing an software.
By conducting load testing early within the growth course of, potential efficiency bottlenecks and scalability points may be recognized and addressed proactively earlier than they impression finish customers.
This proactive strategy not solely helps in delivering a dependable and environment friendly software program product but additionally enhances the general person expertise.
Moreover, even smaller functions can profit from load testing because it supplies helpful insights into their efficiency capabilities and limitations beneath disturbing conditions. Common load testing helps in sustaining and enhancing the efficiency of the software program, making certain it might deal with real-world utilization situations successfully.
Load testing ought to be integrated from the early phases of growth and executed recurrently, not simply earlier than main launches or when points come up. Key causes embody:
- Detect efficiency points early earlier than they impression actual customers. Do not await person complaints.
- Perceive the efficiency profile and set baseline metrics to catch regressions over time.
- Guarantee the appliance stays performant as new options are added.
- Permit time to optimize and repair points. Efficiency should not be an afterthought.
- Construct a efficiency tradition the place it is everybody’s accountability.
Load Testing vs. Different Check
Load testing vs. different checks is among the most misunderstood elements of efficiency testing. And there are lots of load testing greatest practices try to be conscious of earlier than even utilizing one of many instruments listed beneath.
Right here is our complete listing of the highest open-source and FREE load testing instruments you need to use this 2024 in your load and stress testing efficiency engineering efforts.
Under are some of the perfect load testing instruments that embody a software comparability that will help you resolve on which one is correct in your software efficiency efforts in 2025.
The Prime Load Testing Instruments Record for 2025
This listing solely contains open supply and free choices for the highest load check software program for automated efficiency testing and API load checks, so you possibly can simply obtain and get began straight away with out spending a dime.
* However earlier than we get to the free choices, if you’re severe about dependable enterprise-wide efficiency load testing, then you definately want a vendor-based resolution. Belief me—I began my profession as a efficiency tester and wouldn’t have been in a position to do my job with no full-scale resolution like WebLOAD.
1. JMeter 
JMeter is the most well-liked open-source load check software program within the efficiency area to assist measure load time.
Apache JMeter describes itself as a Java software that was designed particularly for load testing with the power to measure software efficiency and response occasions.
JMeter was constructed to be the open-source different to LoadRunner, so that you’ll discover it has many refined options. It is a thick shopper Java app that is largely pushed by proper clicks. It is slightly bizarre, however it’s received a number of energy. Additionally, all of the contains a skilled load tester desires can be found on JMeter.
Key Options
- The flexibility to efficiency check a bunch of applied sciences utilizing a spread of protocols similar to Java Objects, Internet HTTP/HTTPS, SOAP and Relaxation Companies, FTP, and Databases with JDBC
- A pleasant IDE you need to use for recording, constructing, and debugging your efficiency checks.
- Beginning with JMeter 3.1, Groovy is the default programming language
- One of many extra in style load testing instruments
- Can configure it to assist check the cell efficiency of cell apps
- Utilizing jmeter-java-dsl, you possibly can write your efficiency checks in Java and reap the benefits of IDEs autocompletion and inline documentation.
It presently has over 8.7k stars on GitHub.
Cons
Though JMeter is among the extra in style load testing instruments, it does have a breaking level, similar to:
As an example, JMeter could be a bit troublesome to scale for a big distributed check, particularly if you need to arrange a bunch of machines since you need to configure them to speak to one another. There may be additionally a bunch of orchestrating issues in executing massive JMeter checks.
That’s the place a software open–sourced by BlazeMeter—Taurus—may help you out.
Automation Testing Coaching Programs
2. Taurus 
Whereas not technically a load testing software, Taurus acts extra like a wrapper on prime of different options that disguise the complexity of working efficiency checks.
The facility of Taurus is that it permits you to write your checks in YAML.
You’ll be able to really describe a full-blown script in about ten traces of textual content, permitting groups to explain their checks in a YAML or JSON file. The YAML is a human, readable, edible strategy that allows you to describe a check in a easy textual content file.
It is a massive leap ahead from the outdated days of getting to deliver up a major, heavy vendor-specific document and scripting software for load time measuring.
Key Options
- This also needs to permit extra staff members to contribute to efficiency checks. Additionally, since your check circumstances are written in YAML, the checks are rather more readable, making them simpler to carry out code opinions.
- Taurus principally suits efficiency testing into your CI/CD pipeline rather more effectively.
- Taurus supplies an abstraction layer on prime of JMeter and another instruments like Locust, Gatling, the Grinder, and Selenium.
It presently has 2.1k stars on GitHub.
3.Locust 
Locust is a simple-to-use, distributed, person load testing software that may assist you seize response occasions. So, what scripting languages does it use?
The very best one — is Python. It’s used to assist efficiency check web sites or different functions.
Locust vs. JMeter
Instruments like JMeter are primarily based upon a thread-based structure that consumes many sources. Alternatively, Locust makes use of an event-based strategy that makes use of fewer sources.
Rahul Solanki, a technical chief at BlueConch Applied sciences, talked about to me that when he in contrast it with JMeter, the variety of sources that Locust occupies was round 70 % much less.
If you happen to’re aware of the time period “load turbines,” Locust makes use of the time period “swarm”–as in you possibly can level a swarm of locusts to place a load in your web site.
You’ll be able to outline the conduct you need for every of your Locust situations. It additionally offers you the power to observe the swarming course of from an online UI in real-time.
Key Options
- The flexibility to create your check situations utilizing straight Python
- You’ll be able to simply scale the variety of customers you should emulate
- It has a pleasant Internet-based UI
- Extensible
- Good for testing APIs
Cons
Since it is a newer software, it has far fewer plugins than JMeter.
It presently has 25.9k stars on GitHub.
4. Fiddler with BlackWidow and Watcher 
This may appear to be an odd mixture on a web site efficiency software listing.
However efficiency engineering knowledgeable Todd DeCapua, in a earlier PerfGuild convention session, really useful utilizing Fiddler with Watcher and BlackWidow to create a quick-start automation testing efficiency resolution.
Fiddler allows you to do many issues, however it’s in all probability greatest described as a packet seize software.
Whereas Fiddler will not be thought-about a load testing resolution, it does many issues that help you debug web site points, and with one in all its many extensions, you possibly can accomplish much more.
Key Options
- Troubleshooting points together with your net software
- Safety testing
- Efficiency evaluations
- Debugging net site visitors from most computer systems and gadgets
- Many integration options
- Useful for locating efficiency bottlenecks
- Fiddler is already a fairly in style software amongst builders. Many use it for debugging to view the HTTP requests their laptop sends to a service or web site.
Watcher is a safety add-in for Fiddler, enabling you to get some safety outcomes rapidly. BlackWidow is an online crawler that offers you the performance to level it in direction of an online handle after which be capable to drill down on outcomes.
For somebody simply getting began in efficiency engineering, these three instruments working collectively can present an effective way to get that free feel and appear and outcomes that one won’t in any other case be capable to receive rapidly.
Todd had a session throughout a previous PerfGuild On-line Convention the place he demoed this strategy.
5. nGrinder 
nGrinder‘s GitHub web page describes it as having been designed to be an enterprise-level efficiency engineering resolution. It was developed to simplify stress testing and supply a platform that permits you to create, execute, and monitor checks.
Key Options
- You’ll be able to write your checks utilizing Jython or Groovy to create check situations and create stress towards JVM utilizing a number of brokers.
- It may possibly prolong checks with buyer libraries like jar and py
- Lets you monitor the state of your efficiency brokers load technology
- Care for routinely amassing check outcomes from distributed brokers after checks
It presently has 2.1k stars on GitHub.
Automation Testing Coaching Programs
6. The Grinder
The Grinder is a Java-based framework. It supplies you with easy-to-run and -create distributed testing options utilizing many load generator machines to seize your end-users response occasions. So you do not have to fret about any digital person restrictions.
Key Options
- You’ll be able to carry out load testing on any system that has a Java API
- A pleasant GUI console
- It routinely handles the administration of shopper connections and cookies
7. Gatling
Gatling is a stress check software constructed on Scala, Akka, and Netty.
This contemporary structure strategy permits you to check and measure your software’s end-to-end efficiency and simply scale up your digital customers’ to-end efficiency and simply scale up your digital customers.
Key Options
- It has a easy but highly effective DSL.
- Straightforward to increase
- If you happen to’re into Scala and its advantages, that is the greatest load testing software for you.
- It has a state of affairs recorder.
- Lets you take a shift-left code strategy to efficiency testing
Two main Updates: Gatling lately introduced is has launched a brand new JavaScript and TypeScript SDK, doubling its accessibility for builders. It additionally has launched enhanced no-code testing capabilities of their newest replace. The brand new options purpose to make efficiency testing extra accessible by permitting customers to create and execute checks with no need to jot down code.
It presently has 6.6k stars on GitHub.
To study extra about Gatling, take a look at the Founding father of Gatling, Stephane Landelle’s PerfGuild session on Load Testing Executed Proper with Gatling.
8. k6
k6 is a developer-centric, open-source load testing software for testing the efficiency of your back-end infrastructure.
It’s also possible to use k6 to start out together with efficiency testing in your steady integration pipelines.
k6 can be a Fashionable load testing software constructed with Go and JavaScript, integrating effectively into most builders’ workflow.
Additionally new for 2023, K6 creates xk6. xk6-browser is an extension for K6, a efficiency testing software. It supplies browser automation and end-to-end net testing capabilities, permitting you to measure each front-end and back-end efficiency utilizing a single software. xk6-browser affords a singular hybrid strategy to efficiency testing by combining protocol-level checks with browser-level checks, supplying you with a extra complete and lifelike view of your net software’s efficiency.
xk6-browser presently helps Chromium, with plans to assist different browsers sooner or later. You’ll be able to work together with web page parts, execute actions, and carry out numerous checks utilizing CSS selectors. The software additionally supplies browser-specific efficiency metrics, similar to DOM content material loaded, first contentful paint, and first significant paint.
Key Options
- Clear scripting API
- Supplies distributed & Cloud Execution
- Cool REST API orchestration potential
- Carry out browser-level front-end efficiency utilizing the brand new xk6 extension.
It presently has 27.2k stars on GitHub.
9. Tsung
Tsung is an open-source, multi-protocol distributed load testing tool.
Key Options
- Can monitor a shopper’s CPU, reminiscence, and community site visitors
- It has an HTTP recorder
- Contains HTML stories and graphs
- Helps protocols like HTTP, XMPP, LDAP, and many others.
It presently has 2.6k stars on GitHub.
10. Siege 
Siege is a command-line HTTP load testing and benchmarking utility. It was designed to assist builders measure their code beneath stress.
Key Options
- Helps primary authentication, cookies, HTTP, HTTPS, and FTP protocols.
- Permits its customers to hit a server with a configurable variety of simulated shoppers. These shoppers place the server “beneath siege.”
- Nice for a easy, brute-force sort of efficiency testing software
It presently has 6.1k stars on GitHub.
11. Bees with Machine Weapons 
The load testing software program was developed by the Chicago Tribune, that is in all probability one in all this listing’s coolest-sounding efficiency testing instruments.
Bees with Machine Weapons describes itself as a utility for arming (creating) many bees (micro Amazon EC2 situations) to assault (load check) targets (net functions).
This load or quantity testing software can rapidly assist you load check a website to deal with excessive site visitors.
Leverage Amazon EC2
It presently has 6.5k stars on GitHub.
LoadRunner tends to be probably the most frequent enterprise-wide load testing instruments, however many of those open-source instruments can get you a lot of the performance you want. Additionally, most of those software protocols can be utilized for each efficiency testing net functions and efficiency testing net providers.
Automation Testing Coaching Programs
12. Fortio
Fortio is a cool load testing library, command-line software, superior echo server, and net UI in GO (golang).
This software permits the specifying of a set query-per-second load and recording latency histograms and different helpful stats.
Execs
- It is quick
- Small footprint (3Mb docker picture, minimal dependencies)
- Reusable
- Embeddable go library
- Can document latency histograms and different helpful stats.
It presently has 3.5k stars on GitHub.
13. puppeteer-webperf
With most trendy functions utilizing javascript heavy front-ends, the want for client-side efficiency measurements has by no means been better.
Do not ignore front-end efficiency.
You should use Puppeteer WebPerf to acquire net efficiency stats like a hint for a web page load, seize a dev instruments hint with screenshots, get runtime efficiency metrics, and a bunch extra.
Additionally, take a look at my full front-end efficiency testing information for more information.
It presently has 1.8k stars on GitHub.
14. Artillery.io
Artillery.io is an open-source software with an opt-in of premium providers to create load checks to simulate load to emulate 1000’s of persons.
- latency
- requests per second
- concurrency
- seize common response time
- and throughput.
I additionally lately discovered that you need to use your Playwright check script as efficiency check integrating with Artillery.
Key Options
- Peak efficiency testing to deal with most site visitors in your back-end software for stability and reliability.
- It has the power to jot down customized logic, put up, and pretest situations utilizing JavaScript, which has all kinds of NPM modules that you need to use.
- It helps a number of protocols, together with HTTP, Internet Socket, Socket.IO, Kinesis, and HLS.
It presently has 7.4 stars on GitHub.
15. Anteon (previously Ddosify)
Now a days you in all probability must take care of efficiency in a Kubernetes setting. That the place Anteon is available in.
Anteon is described as an open-source, eBPF-based Kubernetes Monitoring and Efficiency Testing platform obtainable on CLI, Self-Hosted, and Cloud. Its primary options embody:
- Kubernetes Monitoring: Automates the creation of service maps in your Kubernetes (K8s) cluster to assist establish system bottlenecks with out the necessity for code instrumentation or sidecars. It supplies efficiency insights, real-time metrics on cluster situations (CPU, reminiscence, disk, and community utilization), alerts for anomalies, and helps distributed tracing.
- Efficiency Testing: Allows multi-location primarily based efficiency testing from over 25 international locations worldwide, with a simple state of affairs builder and Postman integration for handy API growth and testing.
- Ddosify Stack: Contains 4 primary parts: Ddosify Engine, Ddosify eBPF Agent (Alaz), Ddosify Self-Hosted, and Ddosify Cloud. The Engine is a CLI load-testing software, written in Golang, that kinds the spine of the platform. Alaz is an eBPF agent that collects Kubernetes service site visitors knowledge. The Self-Hosted and Cloud variations provide web-based interfaces for efficiency testing and Kubernetes monitoring.
Anteon goals to supply easy Kubernetes monitoring and efficiency testing, making it simpler to identify and resolve points inside K8s clusters. The platform emphasizes ease of use, requiring no code modifications, service restarts, or extra parts to achieve insights, facilitated by the eBPF-based agent Alaz. It alerts customers to uncommon actions, like sudden will increase in CPU utilization, and integrates efficiency testing with Kubernetes monitoring for a unified expertise.
It presently has 8.5 stars on GitHub.
Earlier than you soar into utilizing any of those instruments listed here are a number of extra issues to contemplate.
How can organizations discover the precise match for his or her staff and use case when choosing load testing instruments?
These are, for my part, the highest 15 efficiency load tester instruments for load testing free choices.
As all the time, choosing the proper load testing software program in your staff’s stress and cargo testing wants will depend on what you should check.
I do know it may be overwhelming choosing a efficiency software however listed here are some tips.
First fastidiously consider your particular necessities and aims. It’s important to contemplate components such:
- Measurement of the staff
- Degree of experience obtainable
- The complexity of the functions being examined, and the specified testing outcomes.
By understanding these key features, organizations can successfully analysis and examine totally different load testing instruments to find out which of them align greatest with their wants.
Moreover, searching for suggestions from trade consultants, studying opinions, and conducting trials or demos of the instruments can even present helpful insights into their efficiency and suitability for the group’s specific circumstances.
Finally, by taking a scientific and knowledgeable strategy to evaluating load testing instruments, organizations could make a well-informed choice that meets the distinctive necessities of their staff and use case.
Organizations ought to consider load testing instruments primarily based on their particular wants and use circumstances. Key issues embody:
- Protocols and applied sciences supported (e.g. HTTP, browser-based, cell, and many others.)
- Ease of use and developer expertise, particularly for getting non-performance engineers concerned
- Capacity to combine with the staff’s present processes and CI/CD pipelines
- Cloud-based and scalability options
- Value and licensing mannequin
It is best to take a “toolbox” strategy and choose the perfect software for every job, slightly than anticipating one software to satisfy all wants. Open-source instruments usually present probably the most flexibility and innovation.
Key practices for an efficient load check utilizing instruments
- Decide clear targets and exit standards upfront. What questions are you attempting to reply?
- Choose lifelike person situations, check knowledge, and environments. Keep away from default or dummy knowledge.
- Perceive your actual manufacturing utilization patterns and volumes to set applicable concurrency, ramp-up, and knowledge scale.
- Use CI/CD integration and cloud scalability options to make load testing automated and scalable.
- Embody community virtualization and client-side efficiency monitoring, not simply server metrics.
- Analyze outcomes to seek out root causes and optimize all layers – server, database, community, client-side, and many others.
- Retest after making fixes to confirm the impression. Proceed monitoring in manufacturing as effectively.
Efficient load testing requires instruments, practices, environments, abilities and a efficiency mindset throughout the staff.
Pleased efficiency testing with these stress testing and cargo check instruments!
Load Testing Instruments FAQ?
Are you overwhelmed with staying present with all of the newest efficiency testing instruments and greatest practices? Hear in to the weekly TestGuild DevOps Toolschain Podcast.
