A Guide to Mock APIs & Roundup of Top 5 Tools (Free & Paid)


Mock APIs, also known as fake APIs, are a useful tool in the arsenal of developers, helping them test their code at various stages during development. One of the biggest reasons Mock APIs have risen in popularity is their ability to cut development time by a significant margin. Because in the initial stages of development, there is little to no scope for testing or running code on a reliable backend. Live data is often unreliable or unavailable during development cycles, especially in the early stages. That said, there’s never an excuse for not testing code and improvising it right from the nascent stages of app development. 

Mock APIs not only let developers test various units of code from the get-go but also bring many other benefits. In this article, we explore Mock APIs, their advantages, prominent use cases, best practices, and mainly, the top six mock API tools, both paid and free to check out.

Read on. 

What are Mock APIs 

Mock APIs are not actual APIs. They return the desired data and are simulated for specific use cases. Mock APIs will have the same schema as a real API. These Mock APIs can run on the local server or a cloud server.

Some Benefits of Mock APIs

The below sections explore some of the top benefits of Mock APIs.

  1. Helps Devs Discover Issues Early-On
    Mock APIs allow developers to test their applications from the early stages of development. Even before integrating with the actual API, developers tend to test it with a Mock API. Doing so can help devs stress test their application by simulating various scenarios. Overall, Mock APIs save dev time by giving the means to predict any issues early on and fix them before deployment.
  2. Enables Front-end & Back-end Devs to Work Simultaneously
    Often, front-end developers wait for back-end teams to build the necessary APIs in the background. With the advent of Mock APIs, front-end devs are no longer blocked by the progress of back-end teams, giving them the agility required to speed up the development process.
  3. Cuts Costs During Development & Testing
    APIs are resource intensive and frequently come with usage limits that can be quite limiting for developers during testing or development. Mock APIs, however, let developers thoroughly test as many scenarios and cases as possible without making costly API calls.
  4. Provides an Extra Layer of Security
    In many cases, APIs tend to contain confidential information that should be protected and not made accessible during testing or development. Using Mock APIs, data remains protected in such cases, and developers still meet their end goals.

Use Cases of Mock APIs

Mock APIs find countless use cases in various stages of the software development lifecycle. Some of the top use cases are listed below.

  1. Development
    As mentioned, developers can use Mock APIs to test their applications when the back-end teams are still developing the API.
  2. Debugging
    Mock APIs produce a predictable response to requests, letting developers debug applications by simulating various error scenarios.
  3. Testing
    Mock APIs can be used instead of actual APIs during the testing phase. Doing so spares developers the trouble of sending real requests as they simply test in a controlled environment using a Mock API.
  4. Load Testing
    Through Mock APIs, developers can test the behavior of the actual API under various loads. Such stress testing allows developers to tweak their real API to handle high-traffic scenarios.
  5. Demonstration
    In cases where the functionality of an API needs to be demonstrated without actually deploying it, a Mock API can be ideally suited. Be it for ideation or feedback. In addition, mock APIs come in handy for developers to demonstrate the behavior of the API they’re building.

Best Practices to Follow While Mocking APIs

It is essential to follow certain best practices to get the best results from using Mock APIs. Below, we share a few aspects to remember while mocking APIs. 

  1. Utilize Mocking Libraries
    Requestly, MockServer and JSONPlaceholder are some of the many options at the disposal of developers, offering extensive mocking libraries. Utilizing such tools simplifies the entire process of creating mock API responses.
  2. Plan for Edge Cases
    If you can plan for edge cases like timeouts, error responses, and other unforeseen scenarios, identifying and fixing issues during production can be circumvented.
  3. Use Version Control
    Remember to save Mock API responses in version control so you can roll back changes and collaborate with other team members seamlessly.
  4. Document Mocks 
    Document Mock API responses thoroughly so others in your team can understand them in the future. 

Top 5 Free & Paid Mock API Tools 

In the sections below, we explore some of the most popular free and paid Mock API tools, giving you their overview, pricing, advantages, and limitations. 


Requestly is an open-source, lightweight tool that lets developers accomplish various things, from redirecting URLS and switching hosts to mocking APIs and delaying network requests. Available in free and paid versions, Requestly can be used as a web application from any latest browser or downloaded as a browser extension to Chrome, Firefox, or Edge. 

Requestly’s Mock Server allows developers to edit and delete Mock API responses without building an API. Besides Mock APIs, Requestly’s Mock Server lets developers write plain HTML, CSS, or JS on their editor and test without deploying. 


Requestly is open source, so a developer can start using the self-hosted version for Free. It also has a subscription plan, but Requestly, unlike other options that will be discussed ahead, doesn’t provide a host of subscription plans to choose from. Instead, it has two plans, one is a free “Basic” plan, and the other is the paid “Team” plan. The team plan is priced at $25 per month per user. Learn more about the pricing and features available under the Basic and Team plan here. Developers looking to choose a hassle-free tool without being overwhelmed by various subscription plans find Requestly incredibly simple and easy to start with. 


  • Great scope for customisation
  • Flexible and easy to user
  • User-friendly features 
  • Responsive & vibrant user community
  • Available as a browser extension 
  • Better collaboration through team workspace


  • Limited mobile support 
  • Requires signing up to create mock APIs 


Available as both a free and paid tool, Postman is one of the most popular API development and testing tools available on the internet. This tool is especially known for its user-friendly interface and simple workflow. From API testing and design to documentation, Postman is widely used by developers and testers alike. 


Postman is available in four versions, a free plan, a basic plan, a pro plan, and an enterprise plan. While the free plan is for individuals or small teams, the basic, pro, and enterprise plans are for increasingly larger teams or organizations. The Basic plan of Postman starts at $12 per user per month if billed annually and $15 per user if billed monthly. On the other hand, the Professional plan starts at $29 per user per month if paid annually and $36 per user if paid monthly. Finally, the Postman Enterprise plan starts at $99 per user monthly, billed annually.


  • User friendly 
  • Easy to access 
  • Supports all HTTP methods
  • Extensive request tracking capability


  • Difficult UX to navigate
  • Limited testing scope 
  • Poor script reusability 
  • Difficulty in integration


Stoplight is a one-stop destination for API design, development, and documentation. The platform is known for its API-first design approach, allowing devs to build quality APIs and collaborate with team members seamlessly. Stoplight’s unified design interface for API development provides greater design consistency, resulting in better quality and easy maintenance. Stoplight API provides holistic tools to develop, document, test, and monitor APIs. 


Available in free and paid versions, Stoplight offers a range of paid plans for teams of all sizes. The basic plan, for instance, starts at $39 per month per user, when billed annually. On the other hand, the professional plan costs up to $319 per month per user, when billed annually. Larger teams looking for a custom enterprise plan can also avail that option with Stoplight.


  • Superior Design Consistency 
  • Comprehensive Documentation 
  • Easy Collaboration 
  • Real-Time Monitoring of APIs 


  • Steep Learning Curve 
  • Constrained Integration 
  • Limited Community Support 
  • Less Scope for API Customization


WireMock is an open-source tool for building Mock APIs. For those looking to start with a free platform, WireMock can be a solid option considering its simple and flexible interface. Developers of all levels can familiarize themselves with WireMock and start using it for mocking HTTP services and creating APIs for testing or demonstration. Options like flexible matching on HTTP headers, request body, custom matches, response templating, and request logging make WireMock a lean yet powerful tool for building Mock APIs. 


WireMock is open source & has a free plan with limitations. Their team plan goes upto $47 per month.


  • Open Source 
  • Simple and Easy to Use 
  • Supports Response Templating 
  • Logs all HTTP Requests 


  • Limited Database Integration
  • Fewer Response Formats 
  • Limited Community Support 
  • Higher Maintenance as its Open Source


Mockoon is a cross-platform, open-source API mocking tool that helps developers create mock APIs and servers for testing and development. The tool is easy to use, supports multiple environments, and allows devs to create custom API routes and responses. Due to supporting multiple environments, Mockoon allows developers to create standalone dev, staging, and production environments. Moreover, even switching between various environments is seamlessly executed on the tool. Due to being open-sourced, Mockoon can be customized to fit the specific needs of devs and organizations. 


Mockoon is a free and open-sourced API mocking tool. While there isn’t any pro version of the tool, it will soon be introduced. On top of the free version, there’s also Enterprise Support, where the monthly price per user is $499.


  • Easy to Use & Customizable 
  • Multiple Environments & Seamless Switching
  • Cross-Platform Availability 
  • Free & Open Source 


  • Performance Issues with Large Request Volumes
  • Limited Community Support
  • High Maintenance Due to Being Open Sourced
  • Lack of Native Database Integration 

How to Choose the Right Mock API Tool 

Choosing the right Mock API tool can do wonders for developer productivity, and vice versa could be true in some cases. It is, therefore, important to carefully consider the factors we list below when choosing a Mock API tool for your team or organization.

  1. Integration Support: Check if the Mock API tool you’re considering integrates seamlessly with your other suite of tools and workflow.
  2. Documentation: Mock API tools with detailed documentation simplify developers’ lives and can be helpful during troubleshooting. 
  3. Ease of Use: The Mock API tool you choose should be easy to use and understand. Tools with steep learning curves end up becoming counterproductive since Mock API tools are utilized to save time in the first place and speed up the development process. 
  4. Customizability & Flexibility: Mock API tools that allow you to customize the API according to your requirements let you create Mock APIs that closely resemble the actual API built for your use case. 
  5. Performance Capability: The Mock API tool you choose should handle high volumes of traffic and load. 

Requestly: A Trusted Choice for Mock APIs 

Whether you’re looking for a paid or free Mock API tool, Requestly has got you covered. The easy-to-use Mock Server by Requestly lets devs develop and test Mock APIs for a range of applications as well as platforms. Be it web apps, mobile apps, or IoT. In addition, you can create Mock APIs using Requestly for various platforms. Available as a web app or a browser extension, Requestly is a trusted choice of several developers across the globe. If you want to learn more about Requestly or get started with our tool immediately, visit https://requestly.com/ today.  

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Sagar Soni

Sagar is the co-founder and CTO of Requestly. When he's not busy architecting the next big thing in software development, you'll likely find him behind the wheel, cruising the streets and enjoying the thrill of the drive. For Sagar, it's all about the code by day and the open road by night.