I built a tool that automatically tracks every free AI API daily — here's how

Every time I wanted to build something with AI, I wasted hours on the same frustrating loop.
Which free APIs actually work? What are the real limits? Do they need a credit card? The documentation lies. The Reddit posts are outdated. You only find out the truth after you've already integrated it.
So I built FreeStack AI to solve this for myself — and every other developer stuck in that loop.
What it does
FreeStack AI tracks 5 free AI APIs in real time — Groq, Mistral, Cohere, Gemini, and OpenRouter. Every 24 hours it automatically tests each one with real API calls, measures response speed, checks availability, and saves the results to a database.
No more guessing. You land on the site and instantly see what's working right now.
How the automation works
The core is a simple node-cron job running on a Node.js backend hosted on Render:
javascriptcron.schedule('0 0 * * *', async () => {
await testAllAPIs();
await saveResultsToDB();
});
Every night at midnight it hits all 5 APIs with real test calls, measures latency, and stores everything in MongoDB. The frontend on Vercel just reads from the database — so the data is always fresh without any manual work.
The hardest part — CORS in production
This one took me an entire day to debug.
Everything worked perfectly locally. The moment I deployed to Vercel + Render, requests were completely blocked. Classic CORS issue between two different production domains.
The fix was straightforward once I understood it — explicitly whitelisting the Vercel frontend URL in the Render backend:
javascriptapp.use(cors({
origin: 'https://freestack-ai.vercel.app'
}));
Local development hides this because everything runs on localhost. Production exposes it immediately. Lesson learned.
What's next
Right now 5 APIs are tracked. I'm expanding to 20+ soon — Together AI, Hugging Face, Replicate, DeepInfra and more.
There's also a code generator built in — select your use case, pick an API, choose your language, and get production ready starter code instantly.
Try it here — freestack-ai.vercel.app
If you've ever wasted time figuring out which free AI APIs actually work, this is built for you.