Tuesday, October 14, 2025

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


Discover your supreme API testing device in seconds

What’s an API?

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

Whereas most practical testing entails testing a person interface like an online web page or a dot internet type, API testing bypasses a person interface and communicates instantly with an utility by making calls to its APIs.

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

  • JMS
  • HTTP
  • Databases,
  • Net companies.

This testing method is typically known as “headless” testing.

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

This straightforward instance is sometimes called 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 surprise which device to make use of for Relaxation and Cleaning soap net service-based testing.

Listed here are a few of the well-liked API testing instruments that can be utilized for Relaxation and Cleaning soap Net Service Testing.

These automation instruments are nice as a result of, many occasions, you may 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 a lot of nice paid choices, listed below are the highest free testing instruments you must try for software program testing.

Postman Mail

Postman Logo

Postman is a relaxation shopper that began off as a Chrome browser plugin however just lately got here out with native variations for each Mac and Home windows. They’ve additionally just lately come out with an AI assistant function known as PostBot.

At a excessive degree, you need to use it to ship a submit request to your net server, and it provides you a response again. It lets you arrange all of the headers and cookies your API expects after which examine the response when it returns.

  • It may be used for each automated and exploratory testing
  • Could 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 just lately change into 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

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. For those who’re a tester, this can be a very tester-focused device that does not require you to know find out how to code. This device has change into so well-liked that we’ve even created two free take a look at information programs to get you on top of things on it shortly.

Karate API Testing Course | Test Guild

Karate is thought for being simple to learn and, thus, very maintainable. That is an usually missed facet 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 studies like every normal Java undertaking
  • A take a look at will be written with none Java information required
  • Assessments are simple to write down, 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

Github starsIt presently has over 8.5k stars on GitHub.

Bruno 

Bruno API Tool Logo

On the lookout for a substitute for Postman? Bruno is a glossy, 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 your current workflows.

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

Github starsIt 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 numerous languages and API sorts, together with:

Step CI presents versatility, permitting configurations by way of YAML, JSON, or JavaScript. Customers can even convey their very own take a look at knowledge or generate pretend knowledge for testing functions. And you’ll carry out different cool assessments utilizing it, like:

  • Fuzz Testing
  • Testing ChatGPT
  • CO2 Testing

One in all its standout options is working a number of assessments concurrently with out compromising efficiency.

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

Github starsIt presently has over 1.4k stars on GitHub.

SoapUI soap

SoapUI API Logo

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

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

Because the free model is open-source, you may truly achieve entry to the total supply code and modify it as wanted.

The free model permits you to:

  • You may simply create customized code utilizing Groovy
  • Drag and Drop Take a look at Creating
  • Can create advanced situations
  • Asynchronous Testing
  • SoapUI’s Mock Service permits you to mimic net companies earlier than they’re carried out.

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

Take heed to Mike Giller of Smartbear speak extra about SoapUI:

 

TraceTest Api Testing Logo

TraceTest

TraceTest takes a novel strategy 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 assessments, claiming to cut 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 habits.
  • Hint-Primarily based Testing: Not like conventional API testing instruments which will focus solely on the request and response, Tracetest makes use of hint knowledge to claim the habits and efficiency of the API and the underlying companies. This consists of the flexibility to claim on the timing of hint spans (e.g., guaranteeing a database span executes inside a sure timeframe) and wildcard assertions throughout widespread forms of actions (e.g., all gRPC return codes ought to be 0).
  • No Want for Mocks or Fakes: Since Tracetest assessments towards actual knowledge and makes use of the precise traces of the system, there isn’t any want for the cumbersome setup of mocks or fakes. This may result in extra correct and dependable assessments.
  • Assist for A number of Take a look at Triggers: Tracetest permits defining assessments by numerous triggers similar to HTTP requests, gRPC requests, and hint IDs. This flexibility accommodates a variety of testing situations and necessities.
  • Visible and Programmatic Take a look at Creation: Assessments will be constructed visually by the Net UI or programmatically by way of 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 assessments APIs but in addition analyzes the standard of OpenTelemetry instrumentation throughout the system. This ensures adherence to requirements and might help enhance observability practices.
  • Complete Hint Evaluation and Validation: Past easy API testing, Tracetest presents 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 strategy, and complete options that transcend conventional API testing, providing a extra holistic view of a system’s habits and efficiency.

Github stars It presently has over 1.1k stars on GitHub.

 

HttpMaster Categorical

HttpMaster Express Logo

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

  • HttpMaster undertaking presents world choices to customise your API request
  • Parameter capabilities allow you to incorporate dynamic knowledge along with your request
  • You should utilize request chaining to leverage request gadgets to incorporate some knowledge from the earlier request with the subsequent request

Relaxation- Assured rest

rest-assured api logo

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
  • Assist BDD Given/When/Then syntax
  • Built-in seamlessly with Java initiatives
  • Most likely the usual for programmatically making a relaxation API testing device script

For those who use Java and need a REST API net companies library you need to use in your framework, Relaxation-Assured is an efficient selection. Bas Dijkstra just lately additionally created a C# model.

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

 

Github stars It presently has over 7k stars on GitHub.

RoboHydra Server 

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 an alternative 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 trying to find “API automation testing,” you will must create a easy proxy server with RoboHydra after which write a take a look at script to carry out the search.

  • You may take a look at many alternative sorts of purchasers
  • Written in Javascript, runs underneath Node 

Get Automation Testing Ideas

 

Pyresttest 

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

  • You may write your take a look at scripts in primary 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 that you must 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 examine if the GitHub API returns a 200 standing code when requesting public repositories.

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

- take a look at:
    title: "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 Plane

Airborne is an open-source Ruby-based framework constructed on high 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 gives a easy and readable DSL (Area-Particular Language) that makes it simple for builders and testers to write down assessments.
  • JSON assist: Airborne is designed with JSON in thoughts, making it simple to parse, validate, and manipulate JSON response our bodies in your assessments.
  • Constructed on RSpec: As Airborne is constructed on high of RSpec, you may 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, similar to checking the presence of particular keys or validating the forms of values in JSON objects.
  • Extensible: You may simply lengthen Airborne by including customized matchers or utilizing current RSpec plugins to boost your API testing expertise

To make use of, all that you must 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, title: :string, full_name: :string)
  finish
finish

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

Github starsIt presently has over 1.1k stars on GitHub.

Citrus Framework 

Citrus API Logo

I am uncertain why extra people aren’t conscious of the Citrus Framework. Citrus is an open-source framework that may show you how to automate integration assessments for nearly any messaging protocol or knowledge format. It has good take a look at outcomes studies as properly.

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

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

 

Github starsIt presently has over 465 stars on GitHub.

ZeroCode

ZeroCode API

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 far more. Zerocode Open Supply allows you to create, change, orchestrate, and keep your automated take a look at circumstances declaratively simply.

Listed here 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 assessments
  • Very simple to write down assessments – so simple as Postman REST-Consumer
  • You may nonetheless do BDD, however with out syntax overhead
  • Efficiency testing – Load/Stress technology is kind of simple, and current assessments will be reused
  • Environment friendly Stories – You are able to do a fuzzy search in addition to filter by any textual content, and observe by writer

Github starsIt presently has over 934 stars on GitHub.

Katalon Studio

Katalon Mobile Automation Frameworks

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

Some advantages of Katalon Studio are:

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

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

 

JMeter

JMeter API testing

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

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 API Logo

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 technique to write API assessments. Tavern lets you create automated API assessments in YAML format, making them simple to learn and keep. Moreover, since Tavern is constructed on high of pytest, you may 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 assessments
    • Helps testing RESTful APIs in addition to MQTT-based APIs

Github starsIt presently has over 1,1k stars on GitHub.

Chakram

Chakram API logo

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

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

Github starsIt presently has over 908 stars on GitHub.

Free TestGuild Programs

For those who learn this far, you would possibly ask your self, “Cannot you additionally use a few of the extra well-liked browser automation testing instruments for API testing?” The reply is YES, as an illustration.

Playwright automation framework

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 good for testing net purposes in a number of browsers, together with Chromium, Firefox, and WebKit. Nonetheless, it’s also possible to 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 (substitute along with your API URL)
  const apiUrl="https://api.instance.com/knowledge";

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

  // Test the response standing and knowledge
  if (response.standing === 200 && response.knowledge) {
    console.log('API Take a look at Handed:', response.knowledge);
  } 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 technique 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 just lately launched to assist

On-Demand API Testing Coaching

What about API testing utilizing Cypress — positive!

Cypress Automation Testing Framework

Cypress for API Testing

Identical 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', () => {
    // Change along with your API URL
    const apiUrl="https://api.instance.com/knowledge";

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

Prime API Testing Instruments Recap

I believe software program testers must embrace APIs this 12 months, which is why I’ve so many classes at this 12 months’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 in all places, so I’ll positively add to this record as time passes.

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

Let’s Discuss!

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