A numerology API for mobile apps

The architecture

Put a thin backend between the app and the API:

iOS / Android app  →  your backend  →  simplenumerologyapi.com
                       (holds the key,
                        caches charts)

Never put the API key in the app. Anything in an app binary can be extracted, and a leaked key spends your quota. Your backend can be one serverless function: it checks that the request comes from a signed-in user, adds the X-API-Key header, and caches the response.

The three screens most numerology apps need

Charts are deterministic, so after onboarding most users cost one request a day: their daily number. See personal year numbers and compatibility for each response.

A backend in a few lines

With a Node.js function (Vercel, Netlify, Cloudflare Workers or Firebase):

export async function POST(request) {
  const user = await requireSignedInUser(request); // your auth
  const { birthdate, date } = await request.json();
  const response = await fetch("https://simplenumerologyapi.com/v1/cycles", {
    method: "POST",
    headers: { "X-API-Key": process.env.NUMEROLOGY_API_KEY, "content-type": "application/json" },
    body: JSON.stringify({ birthdate, date }),
  });
  return new Response(await response.text(), { status: response.status });
}

The app calls your function with the user’s birthdate and date from the device clock, so “today” is the user’s today. More on calling the API from JavaScript is in the JavaScript quickstart.

Typed models for Swift and Kotlin

The OpenAPI 3.1 spec generates Codable structs for Swift and data classes for Kotlin or Dart, so the chart fields are typed in the app. Two things to model correctly: number fields can hold the master numbers 11, 22 and 33, and hidden_passion_number is a list.

Frequently asked questions

Can my mobile app call the numerology API directly?

It can technically, but it should not: the API key would ship inside the app, where anyone can extract it. Call the API from a small backend or serverless function that holds the key.

How many requests does a numerology app use?

One chart per user at sign-up, then about one cycles request per active user per day if you cache by day. The free plan’s 100 requests suit development; Starter’s 10,000 a month covers a few hundred daily users, and Pro’s 500,000 about 15,000.

Does it work with Flutter and React Native?

Yes. The app talks to your backend over plain JSON, so any framework works. Dart and TypeScript models can be generated from the OpenAPI spec.

Are my users’ birthdates stored by the API?

No. Names and birthdates are used to compute the response and are never stored or logged.