Top Free API Mocking and Testing Tools for Development

The best free API mocking and testing tools include MockAPI for auto-generated REST endpoints, Keploy for automated test recording, and Requestly for in-browser request interception, all offering generous free tiers suitable for development workflows.

API mocking and testing tools enable developers to build and verify integrations without relying on production backends. The ripienaar/free-for-dev repository maintains a curated list of SaaS platforms that provide robust free tiers for these exact needs. Below is a detailed breakdown of the top free API mocking and testing tools available, sourced directly from the community-maintained registry.

Best Free API Mocking Services

MockAPI – Auto-Generated REST Endpoints

MockAPI delivers a quick-to-use REST-ful mock server that lets you define resources via a UI and automatically generates CRUD endpoints.

• Core capabilities: Auto-generated endpoints, persistent data per project, and built-in support for pagination, filtering, and sorting.
• Free tier: One project with two resources is free forever, making it ideal for small prototypes and teaching labs.
• Source: Listed at line 306 in [README.md](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L306).

Mockerito – Zero-Friction Mock Data

Mockerito offers realistic mock data across nine domains—including e-commerce and finance—without requiring sign-up or API keys.

• Core capabilities: Domain-specific data generators, unlimited requests, and simple JSON responses.
• Free tier: Zero friction with no account required; realistic payloads help front-end developers test UI logic instantly.
• Source: Referenced at line 307 in README.md.

Mockfly – Developer-Focused Mock Platform

Mockfly combines mock-API functionality with feature-flag management through an intuitive dashboard.

• Core capabilities: GUI for endpoint definition, request logging and inspection, and feature-flag toggles.
• Free tier: 500 requests per day with full UI access, suitable for low-volume CI pipelines.
• Source: Documented at line 308 in README.md.

Mocko.dev – Proxy-Based Recording

Mocko.dev operates as a proxy-based mock service that can forward real traffic or return static JSON, making it useful for integration testing.

• Core capabilities: Proxy mode for record-then-replay workflows, custom response scripts, and traffic inspection.
• Free tier: Supports unlimited mock endpoints and traffic recording, ideal for end-to-end test suites.
• Source: Found at line 309 in README.md.

Keploy – Automated Test Generation

Keploy is a functional-testing toolkit that records live API calls and automatically generates KTests (E2E tests) and KMocks (stubs).

• Core capabilities: Auto-recording of HTTP traffic, generation of Go test code, and support for Docker and Kubernetes environments.
• Free tier: Free for open-source projects; eliminates manual test-case writing while keeping mocks synchronized with real APIs.
• Source: Located at line 553 in README.md.

Requestly – In-Browser Request Interception

Requestly functions as a Chrome extension that intercepts, redirects, and mocks HTTP requests directly from the browser.

• Core capabilities: In-browser request editing, mock server functionality, debugging tools, and rule-based redirects.
• Free tier: Up to 10 rules, perfect for quick UI debugging without deploying a separate server.
• Source: Listed at line 560 in README.md.

Mockable.io – REST and SOAP Support

Mockable.io provides a configurable service to mock both REST and SOAP endpoints with instant HTTPS URLs.

• Core capabilities: Support for JSON and XML formats, exportable mock definitions, and HTTPS endpoints.
• Free tier: Unlimited mock endpoints, suitable for front-end and back-end contract testing.
• Source: Appears at line 1493 in README.md.

Mockaroo – Realistic Data Generation

Mockaroo serves as a data-generation platform that can also serve generated datasets as a mock API.

• Core capabilities: Up to 1,000 rows per download, custom schemas, and multiple export formats including CSV, JSON, and SQL.
• Free tier: 200 API calls per day, excellent for generating realistic datasets on-the-fly.
• Source: Referenced at line 1494 in README.md.

Mocklets – Lightweight HTTP Simulator

Mocklets provides a lightweight HTTP-based mock API simulator with a permanent free tier.

• Core capabilities: Unlimited requests, simple JSON response editor, and URL-based versioning.
• Free tier: Lifetime free access makes it a go-to solution for quick proof-of-concepts.
• Source: Documented at line 1495 in README.md.

Quick Start Code Examples

Below are minimal implementations demonstrating how to integrate three of the most versatile tools into your workflow.

MockAPI with JavaScript Fetch

// Create a new resource (e.g., a todo item)
await fetch('https://5f1d-34-78-212-34.ngrok.io/api/v1/todos', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ title: 'Buy coffee', completed: false })
});

// Retrieve the list of todos
const resp = await fetch('https://5f1d-34-78-212-34.ngrok.io/api/v1/todos');
const todos = await resp.json();
console.log(todos);

Replace the base URL with the one generated for your specific MockAPI project.

Mockerito with cURL

# Get a random e-commerce product from Mockerito's free endpoint

curl https://run.mocky.io/v3/8c4c5e2a-7c7b-4e6a-9e9c-8b2f3e7f0c1d

This returns a static JSON payload mimicking a product catalog; swap the URL for any of Mockerito's domain-specific endpoints.

Keploy in Go Tests

package main

import (
    "testing"
    "github.com/keploy/go-sdk/keploy"
)

func TestUserAPI(t *testing.T) {
    // Initialise Keploy recorder
    keploy.Start(t)

    // Your real HTTP client call (will be recorded)
    resp, err := http.Get("https://jsonplaceholder.typicode.com/users/1")
    if err != nil { t.Fatal(err) }
    defer resp.Body.Close()

    // Keploy will automatically generate a KTest that includes a KMock
    keploy.Stop()
}

Running this test creates a KTest file in keploy/tests/ that can be replayed to mock the external API without network traffic.

Source Reference

All tools referenced above are cataloged in the primary source file of the repository:

• [README.md](https://github.com/ripienaar/free-for-dev/blob/master/README.md) – Contains the complete, up-to-date table of free services. Specific entries are located at the following line anchors:
  • MockAPI – #L306
  • Mockerito – #L307
  • Mockfly – #L308
  • Mocko.dev – #L309
  • Keploy – #L553
  • Requestly – #L560
  • Mockable.io – #L1493
  • Mockaroo – #L1494
  • Mocklets – #L1495

Summary

• MockAPI and Mockfly provide UI-driven mock servers with generous free tiers for prototype development.
• Keploy uniquely automates test generation by recording live traffic into replayable test cases.
• Requestly enables rapid browser-side debugging without backend deployment.
• Mocko.dev and Mockable.io support unlimited endpoints for high-volume integration testing.
• All entries are verified in the ripienaar/free-for-dev repository, ensuring current information on free-tier limits.

Frequently Asked Questions

What is the best free API mocking tool for front-end development without registration?

Mockerito requires no sign-up or API key, offering immediate access to realistic mock data across multiple domains. This zero-friction approach allows front-end developers to test UI logic against JSON payloads instantly.

Which free tool should I use for recording and replaying API calls in CI/CD pipelines?

Mocko.dev provides unlimited mock endpoints and traffic recording capabilities on its free tier, making it ideal for end-to-end test suites. Alternatively, Keploy automatically generates test code from recorded traffic, seamlessly integrating into Go-based CI pipelines.

Can these free tools handle SOAP APIs or only REST?

Mockable.io explicitly supports both REST and SOAP endpoints, offering JSON and XML response formats with HTTPS endpoints. While most tools focus on REST, Mockable.io's free tier includes unlimited mock endpoints for SOAP contract testing.

How do the free tiers of API mocking tools typically limit usage?

Limitations vary by service: MockAPI restricts projects to one account with two resources, Mockfly imposes a daily cap of 500 requests, Requestly allows up to 10 redirect rules, and Mockaroo provides 200 API calls per day. Most free tiers remain sufficient for individual development and small team prototyping.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}