🚀 10 Best Free API Testing Tools You Should Use in 2025

API testing is crucial for building reliable applications, but why pay when you can use powerful free tools?

Whether you're a developer, tester, or DevOps engineer, these free API testing tools will streamline your workflow and boost productivity.

✅ 1. Postman (Free Plan)

📌 Website: https://www.postman.com/

🔹 A user-friendly API platform that supports REST, SOAP, and GraphQL.

🔹 Free tier includes API testing, automation, and monitoring.

🔹 New in 2025: AI-powered test generation for faster scripting.

✅ 2. Hoppscotch

📌 Website: https://hoppscotch.io/

🔹 A lightweight, web-based alternative to Postman.

🔹 Supports REST, GraphQL, and WebSockets.

🔹 Open-source and completely free.

✅ 3. Insomnia (Community Edition)

📌 Website: https://insomnia.rest/

🔹 A clean, minimal API testing tool with great UI.

🔹 Supports REST, GraphQL, and gRPC.

🔹 Free version includes environment variables and automated requests.

✅ 4. Karate DSL

📌 GitHub Repo: https://github.com/karatelabs/karate

🔹 Open-source API testing framework with built-in performance testing.

🔹 Supports REST, SOAP, and GraphQL.

🔹 Ideal for automation & CI/CD integration.

🔹 Example Test Case in Karate:

Feature: Test API with Karate 

Scenario: Verify GET request 
    Given url 'https://jsonplaceholder.typicode.com/posts/1' 
    When method GET 
    Then status 200 
    And match response.id == 1 

✅ 5. REST Assured (Java-based)

📌 Website: https://rest-assured.io/

🔹 Java library for testing REST APIs.

🔹 Works well with JUnit, TestNG, and Spring Boot.

🔹 Ideal for backend developers.

🔹 Example API Test with REST Assured:

import static io.restassured.RestAssured.*; 
import static org.hamcrest.Matchers.*; 

public class APITest { 
    public static void main(String[] args) { 
        given() 
            .when().get("https://jsonplaceholder.typicode.com/posts/1") 
            .then().statusCode(200) 
            .body("id", equalTo(1)); 
    } 
} 

✅ 6. Tavern (For Python Testers)

📌 Website: https://taverntesting.github.io/

🔹 API testing tool for Python developers.

🔹 Integrates with Pytest for powerful automation.

🔹 Supports REST and MQTT.

✅ 7. Swagger Inspector

📌 Website: https://swagger.io/tools/swagger-inspector/

🔹 Free online API testing tool from Swagger.

🔹 Helps generate OpenAPI documentation.

🔹 No installation required – works directly in the browser.

✅ 8. Katalon Studio (Free API Testing)

📌 Website: https://www.katalon.com/api-testing/

🔹 GUI-based API testing tool with built-in automation.

🔹 Free for individuals and small teams.

🔹 Supports REST, SOAP, and GraphQL.

✅ 9. PyRestTest

📌 GitHub Repo: https://github.com/svanoort/pyresttest

🔹 A lightweight, command-line API testing tool for Python.

🔹 Ideal for performance testing.

🔹 Supports JSON validation and automation.

✅ 10. SoapUI (Free Version)

📌 Website: https://www.soapui.org/

🔹 Open-source tool for SOAP and REST API testing.

🔹 Supports functional, security, and performance testing.

🔹 Free version includes most features except API mocking & advanced reporting.

💡 Which One Should You Use?

🔹 Postman & Hoppscotch – Best for everyday API testing.

_ 🔹 Karate & REST Assured_ – Great for automated & performance testing.

_ 🔹 Insomnia & Swagger Inspector_ – Lightweight and easy-to-use tools.

🔹 Tavern & PyRestTest – Perfect for Python-based API testing.

💬 Which free API testing tool do you use?

Drop your recommendations in the comments!

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