APIs power modern applications. Testing them is essential. Paid tools like Postman Pro can be expensive, but free alternatives cover most needs.
Here are 10 free API testing tools for developers.
1. Postman (Free tier) – Industry Standard
URL: https://www.postman.com
Postman is the most popular API client. The free tier includes unlimited API requests, collections, workspaces, and request history. You can organize requests into collections, add tests, and automate workflows. The free version is more than enough for individual developers.
2. Insomnia – Open‑Source API Client
URL: https://www.baike300.com/article/152.html
Insomnia is open‑source and supports GraphQL, gRPC, and WebSockets. The free version includes unlimited requests, environment variables, and plugin support. The interface is less cluttered than Postman – good for developers who prefer simplicity.
3. Hoppscotch – Lightweight Web‑Based
URL: https://hoppscotch.io
Hoppscotch is a free, open‑source, web‑based API client. No installation needed – just open your browser. Supports GraphQL, WebSockets, and server‑sent events. Lightweight and fast. Good alternative to Postman.
4. Bruno – Open‑Source Postman Alternative
URL: https://www.baike300.com/article/153.html
Bruno is a new open‑source API client that stores collections locally. No cloud sync, no accounts – your data stays on your machine. Supports most HTTP methods and environments. Good for privacy‑conscious developers.
5. Thunder Client – VS Code Extension
URL: Built into VS Code Marketplace
Thunder Client is a lightweight API testing tool that runs inside VS Code. No need to switch between applications. Supports collections, environment variables, and GraphQL. Free for basic use.
6. Swagger UI – API Documentation + Testing
URL: https://www.baike300.com/article/154.html
Swagger UI generates interactive API documentation from OpenAPI specifications. Users can test endpoints directly from the documentation page. Free and open‑source. Widely adopted for API documentation.
7. Stoplight (Free tier) – API Design + Testing
URL: https://stoplight.io
Stoplight helps you design, document, and test APIs. The free tier includes API design with OpenAPI, visual editors, and mock servers. Good for planning APIs before writing code.
8. Beeceptor – Mock API Server
URL: https://beeceptor.com
Beeceptor creates mock API endpoints instantly. You can simulate responses, delay responses, and inspect incoming requests. The free tier includes 50 requests per day. Good for prototyping when the backend isn't ready.
9. httpbin – HTTP Request Testing
URL: https://httpbin.org
httpbin is a simple HTTP request and response service. It returns data about your request: headers, IP, user‑agent, etc. Free, open‑source, and invaluable for testing HTTP clients and webhooks. No registration required.
10. Webhook.site – Webhook Testing
URL: https://webhook.site
Webhook.site gives you a unique URL to catch and inspect webhooks. See the raw payload, headers, and timing. The free tier includes 100 requests per day. Good for testing webhook integrations.
More resources: Check our technical tutorials or VPS reviews.