When it comes to building, testing, and managing APIs, there are many tools out there. However, not all come free of cost, and finding the right free API development tool for your needs can be tricky. In this article, I’ll share the top free tools that you can use to make your API development smoother and more efficient, without spending a dime.

1. Postman (Free Tier)

Postman is one of the most popular API development tools for designing, testing, and documenting APIs. The free tier offers a range of features for personal use, including the ability to send HTTP requests, inspect responses, and create API collections.

• Key Features: API design, testing, monitoring, and documentation.
• Use Case: Ideal for testing REST and GraphQL APIs.
• Link: Postman

2. Insomnia (Free Version)

Insomnia is a simple but powerful API client for developers who want a clean UI and efficient workflows. The free version provides essential tools for API testing, including support for REST, GraphQL, and even gRPC APIs.

• Key Features: REST, GraphQL, and environment variables.
• Use Case: Great for quick API testing and development.
• Link: Insomnia

3. Hoppscotch

Hoppscotch (formerly Postwoman) is a fast, free, and lightweight API testing tool that works in the browser. It supports REST, GraphQL, and WebSocket protocols and is fully open-source, making it a go-to choice for developers looking for simplicity.

• Key Features: API testing, environment variables, collections.
• Use Case: Perfect for lightweight and fast API requests.
• Link: Hoppscotch

4. Swagger (OpenAPI)

Swagger offers a suite of open-source tools that help developers design, build, and document APIs based on the OpenAPI specification. It's highly regarded for generating interactive documentation and client SDKs for APIs.

• Key Features: API design, documentation, and testing based on OpenAPI standards.
• Use Case: Best for developers using OpenAPI specs.
• Link: Swagger

5. Apidog (Free Tier)

Apidog is an all-in-one API development platform that combines design, debugging, testing, and documentation into a single tool. The free tier offers all essential features for individuals or small teams.

• Key Features: API design, testing, debugging, mocking, and documentation.
• Use Case: Great for teams needing collaborative API development.
• Link: Apidog

6. HTTPie (Free Version)

HTTPie is a command-line HTTP client that offers an intuitive way to make API requests. With a focus on simplicity, it provides readable output that helps developers quickly debug APIs.

• Key Features: Command-line interface, clear HTTP responses, supports JSON.
• Use Case: Perfect for terminal-based API testing.
• Link: HTTPie

7. SoapUI (Open Source Version)

SoapUI is one of the oldest and most powerful tools for API testing, supporting both REST and SOAP APIs. While the Pro version offers advanced features, the free open-source version is still great for basic functional and load testing.

• Key Features: Functional and performance testing for SOAP and REST APIs.
• Use Case: Ideal for those working with SOAP APIs.
• Link: SoapUI

8. Karate DSL

Karate DSL is an open-source API testing framework that allows you to write tests in a domain-specific language (DSL). It’s popular for both REST API testing and load testing, with built-in support for CI/CD integrations.

• Key Features: DSL-based testing, CI/CD pipeline integrations.
• Use Case: Great for teams that need automated API testing.
• Link: Karate DSL

9. Redoc (Free)

Redoc is an open-source tool that generates interactive API documentation from OpenAPI specifications. It’s widely used by developers to provide clear and beautiful API docs, which can be hosted alongside your API.

• Key Features: API documentation generation.
• Use Case: Perfect for anyone looking to generate API docs from OpenAPI specs.
• Link: Redoc

10. Thunder Client (VS Code Extension)

Thunder Client is a lightweight API client built as a VS Code extension. It allows you to send HTTP requests, test APIs, and inspect responses, all from within your code editor.

• Key Features: REST and GraphQL API testing within VS Code.
• Use Case: Ideal for developers who want to test APIs without leaving their code editor.
• Link: Thunder Client

11. RapidAPI (Free Tier)

RapidAPI is both a marketplace and development tool for APIs. You can browse, test, and connect to thousands of public APIs, as well as monitor your own APIs. The free tier provides essential tools for small projects and individual developers.

• Key Features: API testing, marketplace, monitoring.
• Use Case: Best for developers consuming multiple APIs.
• Link: RapidAPI