API Testing Instruments for 2025 (Free & Open-Supply)

Fast Comparability: Finest API Testing Instruments (Up to date Oct 2025)

Scan the necessities beneath, then bounce to full opinions for particulars and code examples.

Instrument	Main Language / Model	License	CLI / CI	Notable Energy	Finest For
Postman	GUI / JS	Free + Paid	Sure	Collaboration & collections	Groups, fast begin
Karate DSL	Java / DSL	Open Supply	Sure	API + UI + perf in a single	Unified testing
Bruno	Recordsdata-as-tests	Open Supply	Sure	Light-weight, Git-friendly	Dev-centric workflows
Step CI	YAML / CLI	Open Supply	Sure	Pipeline-first design	CI/CD pipelines
SoapUI	GUI	OSS + Professional	Sure	SOAP + REST maturity	Legacy SOAP + REST
TraceTest	Config / CLI	Open Supply	Sure	Hint-based testing	Distributed methods
HttpMaster Specific	GUI (Home windows)	Free	Fundamental	Straightforward request suites	Guide + mild auto
Relaxation-Assured	Java	Open Supply	Sure	Fluent API for HTTP	Java automation
RoboHydra Server	Node.js	Open Supply	Sure	Mock/proxy server	Service virtualization
Pyresttest	YAML / Python	Open Supply	Sure	Easy declarative exams	Fast API checks
Airborne	Ruby	Open Supply	Sure	RSpec type	Ruby retailers
Citrus Framework	Java	Open Supply	Sure	Messaging (JMS/HTTP)	Enterprise messaging
ZeroCode	Java / JSON	Open Supply	Sure	Low-code contracts	Contract exams
Katalon Studio	Groovy/GUI	Free + Paid	Sure	All-in-one suite	QA groups
JMeter	Java	Open Supply	Sure	Perf + purposeful	API load & smoke
Tavern	Python / pytest	Open Supply	Sure	YAML + pytest plugins	Python automation
Chakram	Node.js	Open Supply	Sure	BDD type assertions	JS initiatives
Playwright (API)	TS/JS/Java/Python/.NET	Open Supply	Sure	API + UI in a single run	Full-stack e2e
Cypress (API)	JavaScript	Open Supply	Sure	Dev-friendly DX	JS-heavy apps

Tip: Click on a device to leap to its full overview. We confirm particulars month-to-month.

 

Discover your perfect API testing device in seconds

What’s an API?

An API is a specification that acts as an interface for software program parts.

Whereas most purposeful testing entails testing a consumer interface like an online web page or a dot web type, API testing bypasses a consumer interface and communicates straight with an software by making calls to its APIs.

API purposeful testing lets you take a look at headless applied sciences like:

• JMS
• HTTP
• Databases,
• Internet providers.

This testing approach is usually known as “headless” testing.

Most headless testing consists of bypassing the UI, sending a request on to an software’s backend or service, and receiving a response whereas validating the response to make sure issues are working as we anticipate them to.

This easy instance is also known as a shopper/server relationship.

A shopper makes a request by asking for a useful resource; the request then goes out and finds a server that may fill that request. The server locates the specified useful resource and sends a response again to the shopper.

Be part of Take a look at Automation Coaching

What API Testing Instruments Can I Use to Automate API Testing?

Since Selenium is only for browser-based testing, you might marvel which device to make use of for Relaxation and Cleaning soap net service-based testing.

Listed below are a few of the common API testing instruments that can be utilized for Relaxation and Cleaning soap Internet Service Testing.

These automation instruments are nice as a result of, many instances, you’ll be able to leverage one take a look at script to assist with API load/stress efficiency testing, API safety testing, and penetration testing.

So let’s get to it.

Though there are lots of nice paid choices, listed below are the highest free testing instruments you must try for software program testing.

Postman 

Postman is a relaxation shopper that began off as a Chrome browser plugin however not too long ago got here out with native variations for each Mac and Home windows. They’ve additionally not too long ago come out with an AI assistant function known as PostBot.

At a excessive stage, you should use it to ship a put up request to your net server, and it offers you a response again. It lets you arrange all of the headers and cookies your API expects after which test the response when it returns.

• It may be used for each automated and exploratory testing
• Will be run on Mac, Home windows, Linux &Chrome Apps
• It has a bunch of integrations, like assist for Swagger & RAML codecs
• Has Run, Take a look at, Doc, and Monitoring Options
• It doesn’t require studying a brand new language

To listen to how Postman is utilized in the actual world for testing video video games, try Amber Race’s TestTalks episode on Testing Video Video games Utilizing API Automation.

CON: Postman’s options have not too long ago turn out to be paid choices, though they nonetheless have a free plan. That is why extra testers are migrating to instruments like subsequent on our lst Karate.

 

Karate DSL 

Karate lets you create a take a look at to sequence calls to any net service (SOPA or REST) and assert that the responses are as anticipated. In case you’re a tester, this can be a very tester-focused device that does not require you to know how one can code. This device has turn out to be so common that we now have even created two free take a look at information programs to get you on top of things on it rapidly.

Karate is understood for being straightforward to learn and, thus, very maintainable. That is an usually neglected side of selecting a take a look at framework as a result of take a look at suites are used for steady integration so long as the API is dwell in manufacturing.

• It has an easy-to-use human-like syntax
• Can run a take a look at and generate experiences like every customary Java mission
• A take a look at may be written with none Java data required
• Exams are straightforward to put in writing, even for non-programmers

Right here is an instance Karate script:

Characteristic: TestGuild search

  State of affairs: Seek for a key phrase on testguild.com
    Given url 'https://www.testguild.com/'
    And driver
    When driver.get
    Then driver.findElementByCss('#s').enter('automation')
    And driver.findElementByCss('.search-submit').click on()
    And driver.waitForUrl('/?s=automation')
    Then driver.titleContains('automation')

Characteristic: TestGuild search State of affairs: Seek for a key phrase on testguild.com

It presently has over 8.5k stars on GitHub.

Bruno

On the lookout for a substitute for Postman? Bruno is a smooth, open-source API shopper designed for testing and inspecting RESTful APIs with a developer-first expertise.

Not like conventional API instruments, Bruno shops requests as plain textual content in your repository, enabling model management, collaboration, and automation by way of your current workflows.

Constructed with velocity and ease in thoughts, Bruno runs offline, helps environments, variables, and collections, and is absolutely appropriate with Git. It’s a robust different for testers and builders searching for a light-weight, Git-native API testing device.

It presently has over 32.6k stars on GitHub.

Step CI

New to our record is Step CI.

This open-source, self-hosted platform is designed to automate API testing throughout varied languages and API sorts, together with:

Step CI provides versatility, permitting configurations through YAML, JSON, or JavaScript. Customers may deliver their very own take a look at information or generate faux information for testing functions. And you may carry out different cool exams utilizing it, like:

• Fuzz Testing
• Testing ChatGPT
• CO2 Testing

Certainly one of its standout options is working a number of exams concurrently with out compromising efficiency.

For these with an OpenAPI specification, exams may be generated straight from it. For extra insights, you must discover Step CI’s official web site, documentation, and GitHub repository.

It presently has over 1.4k stars on GitHub.

SoapUI 

SoapUI is a headless purposeful testing device from SmartBear software program. It is available in two flavors:

1. Free, open-source model 
2. Professional Model

For the reason that free model is open-source, you’ll be able to really acquire entry to the total supply code and modify it as wanted.

The free model helps you to:

• You’ll be able to simply create customized code utilizing Groovy
• Drag and Drop Take a look at Creating
• Can create advanced eventualities
• Asynchronous Testing
• SoapUI’s Mock Service helps you to mimic net providers earlier than they’re carried out.

The SoapUI Professional model is user-friendly and has extra performance, together with a type editor, an assertion wizard for XPath, and an SQL question builder.  

Hearken to Mike Giller of Smartbear discuss extra about SoapUI:

 

TraceTest

TraceTest takes a singular method to API Testing in comparison with the opposite api automation testing instruments open-source listed right here.

The innovation it brings is that it using OpenTelemetry and trace-based testing.

This device is designed to considerably velocity up the method of making integration and end-to-end exams, claiming to scale back the time required from days to minutes. This is the way it differentiates itself from different API testing instruments on our record:

• Integration with OpenTelemetry: Tracetest leverages OpenTelemetry to seize traces of API calls and their interactions inside a system. This integration permits for a extra in-depth evaluation and testing of the API and the system’s conduct.
• Hint-Based mostly Testing: Not like conventional API testing instruments that will focus solely on the request and response, Tracetest makes use of hint information to say the conduct and efficiency of the API and the underlying providers. This contains the flexibility to say on the timing of hint spans (e.g., making certain a database span executes inside a sure timeframe) and wildcard assertions throughout frequent sorts of actions (e.g., all gRPC return codes needs to be 0).
• No Want for Mocks or Fakes: Since Tracetest exams towards actual information and makes use of the precise traces of the system, there is no such thing as a want for the cumbersome setup of mocks or fakes. This may result in extra correct and dependable exams.
• Help for A number of Take a look at Triggers: Tracetest permits defining exams by way of varied triggers corresponding to HTTP requests, gRPC requests, and hint IDs. This flexibility accommodates a variety of testing eventualities and necessities.
• Visible and Programmatic Take a look at Creation: Exams may be constructed visually by way of the Internet UI or programmatically through YAML, making it accessible for each builders and testers. Moreover, the Tracetest CLI and YAML-based take a look at definition information assist GitOps workflows and CI/CD automation.
• OpenTelemetry Instrumentation Evaluation: Tracetest not solely exams APIs but in addition analyzes the standard of OpenTelemetry instrumentation throughout the system. This ensures adherence to requirements and will help enhance observability practices.
• Complete Hint Evaluation and Validation: Past easy API testing, Tracetest provides options for detailed hint evaluation and validation, imposing OpenTelemetry guidelines and requirements. This may be essential for methods relying closely on distributed tracing for observability.

Tracetest’s distinctive worth proposition lies in its integration with OpenTelemetry, trace-based testing method, and complete options that transcend conventional API testing, providing a extra holistic view of a system’s conduct and efficiency.

It presently has over 1.1k stars on GitHub.

 

HttpMaster Specific

HttpMaster describes itself as an online growth and take a look at device to automate the testing of internet sites and providers. It may be used to check RESTful net providers and API purposes. HttpMaster additionally permits you to watch API responses.

• HttpMaster mission provides international choices to customise your API request
• Parameter capabilities allow you to incorporate dynamic information along with your request
• You should use request chaining to leverage request objects to incorporate some information from the earlier request with the subsequent request

RestAssured 

Relaxation-Assured is an open-source Java Area-specific language (DSL) that simplifies guide testing of REST service. It simplifies issues by eliminating the necessity to use boilerplate code to check and validate advanced responses. It additionally helps XML and JSON Requests/Responses. That is most likely the best-known device to check relaxation API.

• Removes the necessity to create boilerplate code required to work together with a relaxation service
• Help BDD Given/When/Then syntax
• Built-in seamlessly with Java initiatives
• Most likely the usual for programmatically making a relaxation API testing device script

In case you use Java and need a REST API net providers library you should use in your framework, Relaxation-Assured is an efficient alternative. Bas Dijkstra not too long ago additionally created a C# model.

Johan Haleby, creator of Relaxation-Assured, shares suggestions and tips for getting began with REST testing with Relaxation-Assured.

 

>RoboHydra Server 

Are you searching for API integration testing instruments?

RoboHydra is a testing device for HTTP-based purchasers (i.e., software program that makes HTTP requests). As a substitute of connecting your clients-under-test to the actual server, you join them to RoboHydra and make RoboHydra reply with no matter you want for every request.

To make use of RoboHydra to carry out, say, navigating to testguild.com and looking for “API automation testing,” you may must create a easy proxy server with RoboHydra after which write a take a look at script to carry out the search.

• You’ll be able to take a look at many alternative sorts of purchasers
• Written in Javascript, runs below Node 

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Pyresttest 

PyRestTest is a Python-based REST testing and API micro-benchmarking API testing device.

• You’ll be able to write your take a look at scripts in fundamental YAML or JSON config information; no code is required
• Returns exit codes on failure
• It solely works on Mac and Linux

it is easy to get began. All it is advisable to do is set up pip set up pyresttest

Then Create a YAML take a look at file that, for instance, the take a look at will test if the GitHub API returns a 200 standing code when requesting public repositories.

---
- config:
    identify: "GitHub API Take a look at"
    timeout: 5
    headers: {'Person-Agent': 'PyRestTest'}

- take a look at:
    identify: "Get public repositories"
    url: "https://api.github.com/repositories"
    methodology: "GET"
    expected_status: [200]

And run the take a look at:

resttest.py https://api.github.com github_api_test.yaml

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Airborne 

Airborne is an open-source Ruby-based framework constructed on prime of RSpec. RSpec is a well-liked behavior-driven growth (BDD) testing framework within the Ruby ecosystem. Airborne simplifies testing RESTful APIs by offering a set of handy strategies and matchers for making HTTP requests and validating responses.

Key options of Airborne:

• Works with Rack purposes like Sinatra and Grape
• Works with APIs written in Rails
• Straightforward to make use of: Airborne supplies a easy and readable DSL (Area-Particular Language) that makes it straightforward for builders and testers to put in writing exams.
• JSON assist: Airborne is designed with JSON in thoughts, making it straightforward to parse, validate, and manipulate JSON response our bodies in your exams.
• Constructed on RSpec: As Airborne is constructed on prime of RSpec, you’ll be able to leverage the total energy of RSpec matchers and its BDD-style syntax.
• Customized matchers: Airborne features a set of customized matchers to validate API responses, corresponding to checking the presence of particular keys or validating the sorts of values in JSON objects.
• Extensible: You’ll be able to simply lengthen Airborne by including customized matchers or utilizing current RSpec plugins to boost your API testing expertise

To make use of, all it is advisable to do is use the next gem information

gem set up airborne
gem set up rspec

Then create a take a look at file github_api_spec.rb:

require 'airborne'

describe 'GitHub API' do
  it 'retrieves public repositories' do
    get 'https://api.github.com/repositories'
    expect_status(200)
    expect_json_types('*', id: :integer, identify: :string, full_name: :string)
  finish
finish

After which run the take a look at: rspec github_api_spec.rb

It presently has over 1.1k stars on GitHub.

Citrus Framework 

I am not sure why extra of us aren’t conscious of the Citrus Framework. Citrus is an open-source framework that may enable you automate integration exams for just about any messaging protocol or information format. It has good take a look at outcomes experiences as effectively.

• Works with REST, SOAP, HTTP, JMS, TCP/IP, and extra
• Create exams utilizing Java or XML
• Mature – has been round some time

For more information on Citrus and integration testing, test out API Integration Automation Testing With Citrus Framework.

 

ZeroCode

ZeroCode describes itself on GitHub as a community-developed, free, open supply, microservices API automation and cargo testing framework constructed utilizing JUnit core runners for HTTP REST, SOAP, Safety, Database, Kafka, and way more. Zerocode Open Supply allows you to create, change, orchestrate, and keep your automated take a look at instances declaratively simply.

Listed below are some advantages of utilizing ZeroCode:

• ZeroCode is constructed on JUnit core runners (no plugins wanted)
• Simply your IDE or any JSON editor is sufficient to drive the exams
• Very straightforward to put in writing exams – so simple as Postman REST-Consumer
• You’ll be able to nonetheless do BDD, however with out syntax overhead
• Efficiency testing – Load/Stress era is kind of straightforward, and current exams may be reused
• Environment friendly Reviews – You are able to do a fuzzy search in addition to filter by any textual content, and observe by creator

It presently has over 934 stars on GitHub.

Katalon Studio

Katalon Studio is an all-in-one take a look at automation resolution that helps net, cellular, and API testing. It provides complete options and a user-friendly interface, making it appropriate for novices and skilled testers. Katalon Studio can be utilized for headless testing to make sure your RESTful and SOAP net providers’ performance, reliability, efficiency, and safety.

Some advantages of Katalon Studio are:

• It is not open-sourced, however it’s free
• It’s a whole package deal and framework. So it’s straightforward to put in and get working
• Small studying curve
• It has performance that lets you take a look at net providers and REST APIs

Hearken to my interview with Raghav Pal to find extra about Katalon Studio.

 

JMeter

As you would possibly already know, JMeter was developed for load testing, however many testers additionally use it for purposeful API testing and as an API load testing device as effectively.

Some advantages of JMeter are:

• Can leverage one script for each API and API Efficiency testing
• JMeter has been round some time, so it is time-tested
• Simply built-in into CI/CD environments

Tavern

Tavern is a pytest plugin, command-line device, and Python library for automated testing of APIs. It is designed for testing RESTful APIs. It makes use of the highly effective pytest testing framework to create a easy, concise, and versatile option to write API exams. Tavern lets you create automated API exams in YAML format, making them straightforward to learn and keep. Moreover, since Tavern is constructed on prime of pytest, you’ll be able to leverage pytest’s superior options and plugins to boost your API testing expertise.

• • Easy, concise, and versatile YAML-based syntax
  • Very easy to get began
  • Extremely customizable for advanced exams
  • Helps testing RESTful APIs in addition to MQTT-based APIs

It presently has over 1,1k stars on GitHub.

Chakram

Chakram is a REST Javascript API testing instruments framework with a BDD testing type and absolutely exploiting guarantees. So you should use it for

• HTTP Assertions
• Chakram absolutely exploits javascript guarantees
• BDD formatting and hooks
• Very extensible

It presently has over 908 stars on GitHub.

Free TestGuild Programs

In case you learn this far, you would possibly ask your self, “Cannot you additionally use a few of the extra common browser automation testing instruments for API testing?” The reply is YES, as an illustration.

Playwright for API testing

You are able to do API testing utilizing Playwright, though Playwright is primarily designed for end-to-end testing of net purposes. Playwright is a Node.js library that automates browser actions, making it excellent for testing net purposes in a number of browsers, together with Chromium, Firefox, and WebKit. Nonetheless, you can even use it with different libraries to carry out API testing.

This is an instance of how one can carry out API testing utilizing Playwright, together with the “axios” library to make API requests:

First, set up the required libraries:

npm init -y
npm set up playwright axios

Create a take a look at file, e.g., api_test.js, and import the required libraries:

const { chromium } = require('playwright');
const axios = require('axios');

Outline an async perform to carry out the API testing:

async perform testAPI() {
  // Launch a browser occasion utilizing Playwright
  const browser = await chromium.launch();
  const context = await browser.newContext();
  const web page = await context.newPage();

  // Navigate to the goal API URL (change along with your API URL)
  const apiUrl="https://api.instance.com/information";

  // Use axios to make an API request
  const response = await axios.get(apiUrl);

  // Test the response standing and information
  if (response.standing === 200 && response.information) {
    console.log('API Take a look at Handed:', response.information);
  } else {
    console.error('API Take a look at Failed:', response.standing, response.statusText);
  }

  // Shut the browser occasion
  await browser.shut();
}

testAPI();

Do not forget that this is only one option to carry out API testing utilizing Playwright. Playwright is a flexible library that may be mixed with many different libraries and frameworks to carry out extra advanced API testing.

Additionally a PW-API-PLUGIN for API testing in Playwright was not too long ago launched to assist

On-Demand API Testing Coaching

What about API testing utilizing Cypress — positive!

Cypress for API Testing

Similar to Playwright, Cypres is a well-liked end-to-end testing framework for net purposes. Though Cypress is especially designed for browser automation and testing net purposes, it additionally provides performance for testing APIs utilizing the cy.request perform.

Right here is an instance of how that may look

describe('API Take a look at', () => {
  it('GET request', () => {
    // Exchange along with your API URL
    const apiUrl="https://api.instance.com/information";

    // Make a GET request utilizing Cypress
    cy.request(apiUrl).then((response) => {
      // Test the response standing and information
      anticipate(response.standing).to.equal(200);
      anticipate(response.physique).to.have.property('information');
    });
  });
});

High API Testing Instruments Recap

I believe software program testers must embrace APIs this yr, which is why I’ve so many classes at this yr’s Automation Guild to assist. Test them out now.

These are the highest instruments I’ve come throughout, however tons of SOAP and REST API take a look at instruments are popping up all over the place, so I’ll positively add to this record as time passes.

If one in every of your favourite API take a look at instruments isn’t listed, please let me know, and I’ll add it.

Let’s Discuss!