How to Use Demo APIs to Level Up Your API Testing Skills

Let’s face it—most mock APIs are useless.

They either return hardcoded nonsense, require weird sandbox logins, or are so shallow they fall apart the second you try to simulate something realistic. If you've ever tried to build or test anything beyond a to-do list, you know what I’m talking about.

That’s why I’m shouting out apiexplorer.io — a free, always-on playground full of fully functional, realistic business APIs. And yeah, I helped build it.

These aren’t toy endpoints. We’re talking about structured, documented, enterprise-style APIs — like:

• CRM
• Billing
• Inventory
• Payments
• Ecommerce
• HR and Task Management

All of them behave like real systems. So you can test like it’s production—without the risk of actually being in production.

What Makes apiexplorer.io Useful?

Here’s what you get out of the box:

• RESTful API endpoints (CRUD ready)
• OpenAPI docs
• Postman collections
• A browser-based API explorer
• A working UI for each API (yes, you can log in and see what the data looks like)
• API key-based auth (no OAuth pain here)

Just sign up, grab your API key, and get to work.

Example:

GET https://demo-api.apiexplorer.io/api/lonti_demo_api_crm/1.0/contact?limit=10
Headers:
  Accept: application/json
  X-Authorization: Bearer YOUR_API_KEY

Simple. Clean. Fast.

Use Case 1: Level Up Your API Testing Skills

Want to learn API testing with Postman? Practicing with curl? Writing unit tests that simulate real error conditions?

apiexplorer.io gives you realistic behavior, not just happy path JSON dumps. Test:

• Authentication headers
• Invalid inputs
• Rate limits
• Filtering, searching, pagination
• Nested relationships

Trust me: It’s way better than mocking up endpoints by hand or spinning up a dummy Express server for the 500th time.

Use Case 2: Prototyping Integrations with Lonti (Optional but Cool)

If you’re using Martini (Lonti’s low-code integration platform), these APIs slot right in. Just import the OpenAPI spec, create a workflow, and boom—you’re running real workflows with real APIs.

Same if you’re building frontends in Bellini—you can bind components directly to these demo APIs and see actual data flowing, live.

That’s next-level prototyping speed.

Use Case 3: Practice Error Handling Like It’s Production

Most API tutorials stop at 200 OK.

In the real world? You’re dealing with:

• 401 Unauthorized
• 422 Validation Errors
• 500 Server Errors
• Unexpected payload shapes

Use apiexplorer.io to simulate all of that—intentionally send bad data and see how your app responds. Train your test suite to handle failure like a champ.

Getting Started

1. Go to apiexplorer.io
2. Create a free account
3. You’ll be redirected to the Lonti Console where your API key is waiting
4. Hit any endpoint with the following headers:

Accept: application/json  
X-Authorization: Bearer YOUR_API_KEY

1. Browse the API Explorer, or start testing in Postman, curl, HTTPie, or your own app

Why We Built It

We’re devs. We got tired of building apps with garbage APIs or waiting for staging environments to be “ready.”

So we built what we needed: realistic, instant, enterprise-grade demo APIs—with the same standards we’d expect from any real backend.

And yeah, it’s free. No catch.

TL;DR:

If you're building, testing, or learning APIs, stop using trash examples.

Go to apiexplorer.io. Get a free key. Test your skills like it’s real life.

Happy hacking! 🚀

Original source: How to Use Demo APIs to Level Up Your API Testing Skills