We Couldn’t Find Any Free Business APIs to Prototype—So We Built Them

How to use apiexplorer.io to prototype your next integration

Let’s be honest: prototyping integrations shouldn’t be this hard.

We’ve all been there. You’re trying to mock up a quick integration, test an automation, or build a front-end demo—and you hit a wall. Not because the tech is tricky, but because there’s nowhere to get realistic business APIs without signing up for something, waiting for approvals, or giving away your email to some sketchy sandbox. It’s 2025. Why is this still a problem?

We got tired of waiting. So we built what we needed: apiexplorer.io.

It’s a free, open API playground full of realistic business APIs you can plug into your low-code tools, test integrations, automate workflows, or build and demo full apps without waiting on backend teams, security reviews, or vendors.

And yes—it was built with Lonti’s API-first, low-code, no-limits stack.

The Problem: Prototyping Business Workflows Shouldn’t Be This Frustrating

You can find fake data APIs out there—JSON Placeholder, ReqRes, maybe a Stripe or Shopify test API if you dig—but they’re either too simplistic or tied to narrow use cases.

Where’s the “I just need a CRM API to test my app” option?

Where’s the “Let me prototype this Salesforce + HubSpot + ERP flow without logging into six systems” tool?

We looked. It didn’t exist. So our team spun up a set of ready-to-use APIs with real-world business structures: Customers, Products, Invoices, Tasks, Orders, Billing, Human Resources—you name it.

We designed it to feel like a real business backend… minus the headaches.

The Solution: Meet apiexplorer.io

Apiexplorer is a playground of mock-but-functional business APIs that behave exactly like you’d expect in production. No brittle endpoints. No dead data. Just real-looking objects and a RESTful structure that lets you go wild.

You want to:

• Build a front-end app with a full CRM back-end? ✅
• Test a workflow that moves invoice data between tools? ✅
• Mock up a sales dashboard without touching a live database? ✅
  Go for it.

Each API comes with:

• A clean REST interface
• CRUD support
• Linked resources (like customer-to-orders relationships)
• Sample data you can update, delete, or expand
• A real-time API explorer so you can browse, test, and copy cURL/JS/fetch snippets instantly
• OpenAPI schema
• Postman collection

And yeah, we made it all open and free. Because we’re developers too, and we know how annoying it is when you can’t get access to an API without signing up for an account with a credit card number or wait to be manually vetted.

Why We Built This on Lonti

When we built apiexplorer.io, we used the exact same tools we give our users.

• Negroni let us model the data in a clean, reusable, API-first way—basically turning data relationships into usable, documented APIs in minutes.
• Martini gave us the backbone: a powerful, low-code environment to host the APIs, add logic, and handle everything from GETs to complex automations.
• Bellini enabled us to create a UI for each API so you can login and view the data like you would in a production SaaS application.

This wasn’t just a “hey let’s build a fun side project.” This was us pressure-testing our own stack—and proving that you can go from concept to integrated prototype in hours, not weeks.

What You Can Do with It

Here’s what people are already using apiexplorer.io for:

• Testing Martini flows with real API endpoints before going live
• Mocking up Bellini apps that feel like real products (because they are)
• Creating data manifests in Negroni, bound to APIs for reporting or transformation
• Teaching API concepts to teams without risking real data
• Speeding up MVPs for clients and internal tools

And of course—saving loads of time.

Try It Out (No Strings Attached)

You don’t need to install anything. Just go to apiexplorer.io, signup for a free account, instantly get your API access credentials, and start playing.

You don’t need to use any of Lonti’s tools to utilize these APIs (but we hope you do). Feel free to use them in any of your projects no matter what the platform. 

Of course, the demo APIs are also a great way to learn and experiment with the Lonti platfor. They are designed to slot right into your Martini or Bellini project. You can even extend them with your own endpoints and logic.

Final Thoughts

We built apiexplorer.io because we were tired of waiting for the “real” backend to be ready. Now, we don’t have to.

If you’re building apps, automations, or integrations—and you just need good APIs to test, learn, or move fast—this tool is for you.

We couldn’t find the APIs we needed.
So we built them.
And now you can use them too.

👉 Check out apiexplorer.io
👉 Explore Lonti’s full platform