API stands for Application Programming Interface software. It is a set of instructions that enables an app to possess the features of another app.

APIs are the base of all modern applications because they let apps communicate without involving the developers, leading to a good user experience.

API testing tools perform API testing to check its functionality, reliability, and performance.

Nowadays, almost all APIs use REST services to send and receive data. There are several free API development tools available in the market to build REST APIs without spending too much money. Using these API testing tools that interact with RESTful web services is necessary to check that your API produces desired output in different conditions.

In this article, we will discuss 11 free web API development and testing tools to build REST APIs.

Most Used Free API Development and Testing Tools

  • Amazon AWS Free Tier and Amazon API Gateway
  • SoapUI
  • IBM Cloud API Management
  • Runscope
  • APImetrics 
  • JsonStub
  • Mockable
  • Httpbin.org
  • BlazeMeter
  • Loader
  • Apigee

Let’s discuss each Web API development and testing tool one by one.

1. Amazon AWS Free Tier and Amazon API Gateway

You can use AWS services free of cost with limited features. Hence it is known as AWS free tier. You can use AWS to test the website or try out services for developers. 

You just have to create an account, and you get access to the AWS Free Tier for 12 months. When this free tier expires, AWS starts charging. If you don’t want to use the paid version, you can continue with the free AWS.

With the help of this rest API testing tool, you can access the latest technologies and innovations in AI and ML. In the free version, you can use Amazon SageMaker, AWS Lambda, Amazon DynamoDB, etc.

2. SoapUI

SoapUI is built for developers and testers; it is the only open-source tool covering the entire testing spectrum. With its user-friendly graphical interface, SoapUI is the entry point for API testing so you can validate REST, SOAP, and GraphQL-based web services with ease. It is used for individuals and users working on a single machine in one environment.

With the help of SoapUI, you can do: 

  • Scriptless functional testing
  • Security testing
  • Load testing
  • API testing
  • Protocol Support

3. IBM Cloud API Management

IBM Cloud API Management lets you create, manage and monitor a cloud-based environment by which you can create, promote and track APIs.

The API Management characteristics:

  • It Manages the operations of the different servers in the API Management environment.
  • Give the tools to interact with the other servers.
  • Analytic functions let you collect and store information about APIs.
  • Stores accurate data of relevant users and manages security protocols.
  • It has assembly functions that permit APIs to integrate with other endpoints.

Along with API management, IBM also offers API connect. IBM created a scalable API platform that lets you create, expose, and manage APIs across clouds. With the help of API connect, you and your customers can power digital applications.

4. Runscope

Runscope is a cloud-based API development tool that enables businesses to test and debug web service APIs. 

You can solve your problems fast with API performance monitoring and testing. With the help of the Runscope API tool, you ensure that your APIs are up and quickly.

Runscope has less downtime, fewer support tickets, and faster time to solve problems. There is no free version of Runscope available, so you have to take a subscription for this tool or use a 14 days free trial.

Be the first to know when an API is down

  • Runscope supports the notification tools your customers are already using, so your customers don’t need to tell you about downtime and breakages.
  • Runscope quickly catches bugs and solves problems fast with the help of API Dashboard and daily API Performance Report before it becomes a significant issue.

5. APImetrics

APImetrics is a powerful API performance tool used to configure calls from multiple cloud data centers and locations quickly. It supports both REST and SOAP.

It gives you insight into APIs, microservices, web services, and other systems that work and interoperate. No matter what sector you’re servicing, APImetrics has the capabilities and functionality to help you understand the quality of the services you use, supply, or need. 

APImetrcis costs $15 per month for critical APIs, and it offers 30000 API calls per month.

Characteristics of APImetrics are:

  • Measure uptime and latency from any location or cloud.
  • Set custom conditions for the pass and fail rates.
  • Automatically deploy individual API calls or workflows to any cloud and any place. 
  • Deploy securely inside your firewall or in custom locations.
  • Configure custom OAuth Tokens with custom scopes to monitor resource access and API Gateway settings.
  •  Create custom interfaces to other products. 

6. JsonStub

JsonStub is used to develop the front end while faking the backend. You can mock an entire backend with minimal coding and easily create custom HTTP resources complete with fake data. 

It ensures that static text can be used for checking APIs endpoints. JsonStub also inquires and displays front-end testing data. It is an advantageous free API for testing tools to Build REST API.

7. Mockable.io

Mockable.io is the simplest application to create and manage RESTful or SOAP APIs.

No coding skills are required to use this tool. You can organize your mocks in the domain by choosing a name, inviting other users, and creating a subdomain when needed. This tool is free with limited features, and for advanced features, it costs $12 per month.

Mockable.io helps you be more productive by providing you with a flexible platform for API-oriented development.

Related:- iOS App Development Tools

8. HTTPBin.org

The HTTPBin API is an open-source API in the sense that you can make calls to it without validating, but since the API is open-source, you can also fork the code behind the API and run it anywhere you want.

In the beginning, you may find HTTPBin can be challenging to wrap your head around, but then you get used to it. It is a type of meta API that responds to the data you send, but it reflects various aspects of the HTTP characteristics.

It teaches you about the fundamental base of APIs while providing an API that is customizable and flexible enough to do a number of exciting things with it.

9. BlazeMeter

BlazeMeter provides a performance testing tool that you then configure to your particular needs, be it in the form of a load test or stress test, or something else. This is where you scale up your test to run across multiple engines and even from various locations worldwide if you like.

This API testing tool allows users to use interactive features like real-time reporting, location-distributed load, and support tests.

BlazeMeter engines run on Taurus and support various open-source testing tools. Upload your own JMX script to run a JMeter test or a Gatling test by uploading a .scala file.

After signup, you get access to the 14-day free trial; after this, you are charged as per your testing requirements.

10. Loader

Loader API development tool allows you to load data from a content provider or other data source for displaying Fragment Activity. Some multiple classes and interfaces may be involved while using the Loader.

The Loader runs on a separate thread and simplifies thread management by providing callback methods when an event occurs. This REST API testing tool helps to monitor changes in the underlying data source.

You can use Loader for free to test up to 10000 clients for a minute.

11. Apigee

Apigee is a platform for developing and directing APIs. It provides an abstraction for your backend service APIs by fronting services with a proxy layer and includes security, rate limiting, quotas, analytics, and much more.

Apigee allows you to provide secure access to your services with a clear-cut API that is consistent across all of your services, irrespective of service implementation. A consistent API:

  • It makes it easy for app developers to utilize your services.
  • Permit you to change the backend service implementation without affecting the public API.
  • Allows you to take advantage of the analytics, developer portal, and other features built into Apigee.

Related:- Best IDE for Python Development

API Development and Testing Tools FAQs


1. What are API development tools?

API is software that helps to communicate the applications with each other. API development tools are testing tools used to build APIs without any hassle. 

2. What is REST vs. SOAP?

SOAP is a web API protocol used to define the basic structure of the messages and methods of communication. In contrast, REST establishes communication between the client and the server.

3. Which tools are best for API?

The best API development tools are Apigee, SoapUI, Katalon, Postman, Tricentis, Assertible, and much more.

Wrapping Up

Different developers use different API testing tools as per their requirements. Finding a perfect tool is challenging, but it is essential to use a tool that can fulfill your project’s needs. 

With the above-mentioned free web API development and testing tools, you can easily build your REST APIs. With the help of these API testing tools, you will find out which one works best for you.