The setup

The server is an Oracle Cloud Always Free ARM instance — 4 cores, 24 GB of RAM, $0 a month. Each API is a small FastAPI app on its own port, kept alive by a simple supervisor script that restarts it if it dies. RapidAPI sits in front as the gateway: it handles keys, quotas, and billing, so I don't have to build any of that myself.

The whole stack costs nothing to run. That was the point. I wanted to learn how real API products work without paying for the lesson.

What I built

The catalog grew in waves over about two weeks:

• A background remover (my first one — it proved the pipeline end to end)
• Utility APIs: screenshots, speech-to-text, text-to-speech, OCR, translation, IP geolocation, live prices
• Validation APIs: email, phone, postal codes, domain health, VAT & IBAN, holidays
• An AI email writer powered by free LLM tiers
• A passive website security scanner — TLS, security headers, exposed-file checks, and a 0–100 score. That one is my flagship.

Every API has a free plan. The paid plans are cheap. The code runs on the VPS; the GitHub repo is the storefront with docs and examples.

The honest numbers

I checked my provider dashboard before writing this:

• 19 APIs live, 1 more (weather) still private
• Paying subscribers: 0
• Revenue: $0.00
• API calls in the last 7 days: 23 — and every single one of them was me, testing my own endpoints during setup

The APIs work. I verified each one end to end through the real RapidAPI gateway, not just locally. The problem is that nobody knows they exist.

What I got wrong

I built first and thought about discovery later. Actually, I didn't think about discovery at all. Listing an API on a marketplace and waiting turns out to be a complete distribution strategy — a bad one.

Two weeks of building, zero weeks of telling anyone. The math is not subtle.

What I'm doing about it

I froze the catalog. No API #20 until people can actually find the first 19. The current plan:

• Submit the APIs to directories and curated lists (one already found my repo on its own and asked to feature it — that email is what woke me up)
• Write posts like this one, with real numbers, including the embarrassing ones
• Keep the free tiers genuinely usable so people who do find the APIs get value fast

Links

• Docs and catalog: https://github.com/hhellll/dev-utility-APIs
• The flagship: Website Security Scanner on RapidAPI (free plan included)

If you've sold APIs through a marketplace before, I'd honestly like to hear what moved the needle for you. "Build more APIs" is the one answer I've already tried.