# Where to Find Free Payment Processing and Billing APIs: 18+ Curated Options

> Discover free payment processing and billing APIs with over 18 options curated in the free-for-dev repository. Explore generous free tiers for your integration needs.

- Repository: [R.I.Pienaar/free-for-dev](https://github.com/ripienaar/free-for-dev)
- Tags: list
- Published: 2026-02-25

---

**You can find free payment processing and billing APIs in the "Payment and Billing Integration" section of the ripienaar/free-for-dev repository, which curates 18+ services including Adapty.io, RevenueCat, and Moesif with generous free tiers ranging from 100 API calls to $10,000 in monthly tracked revenue.**

The ripienaar/free-for-dev repository is a community-curated index of SaaS, PaaS, and IaaS offerings that provide free tiers for developers. Within its comprehensive catalog, the **Payment and Billing Integration** section specifically lists free payment processing and billing APIs that allow startups to handle subscriptions, currency conversion, and fraud detection without upfront costs.

## Free Payment Processing and Billing APIs in free-for-dev

The repository's [`README.md`](https://github.com/ripienaar/free-for-dev/blob/main/README.md) file contains the curated list between lines 1576 and 1589, organizing services into functional categories. Below is the breakdown of available services by use case.

### Mobile Subscription Management APIs

These services provide backend infrastructure for handling in-app purchases and recurring billing across iOS, Android, and cross-platform frameworks.

- **Adapty.io** – Mobile in-app subscription SDK supporting iOS, Android, React Native, Flutter, Unity, and Web. The free tier covers up to **$10,000** in monthly revenue. Located at [README line 1576](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1576).

- **RevenueCat** – Backend service for iOS and Android in-app purchases and subscriptions. Offers a free tier up to **$2,500** in monthly tracked revenue. Located at [README line 1588](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1588).

- **Qonversion** – Cross-platform subscription management with analytics and A/B testing capabilities. Free tier supports up to **$10,000** in tracked revenue. Located at [README line 1587](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1587).

### Currency Conversion and Exchange Rate APIs

These services provide real-time and historical foreign exchange rates for multi-currency applications.

- **Currencyapi** – Simple currency conversion API offering 300 requests per month (10 requests per minute). Located at [README line 1578](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1578).

- **exchangerate-api.com** – Easy-to-use JSON conversion API with 1,500 requests per month and daily updates. Located at [README line 1582](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1582).

- **currencylayer** – Reliable exchange rate service providing 100 requests per month. Located at [README line 1581](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1581).

- **CurrencyApi (currencyapi.net)** – Live rates for fiat and crypto in JSON and XML formats, offering 1,250 requests per month. Located at [README line 1579](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1579).

- **CurrencyFreaks** – Current and historical exchange rates with 1,000 requests per month on the Developer plan. Located at [README line 1580](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1580).

- **FxRatesAPI** – Real-time and historical FX rates requiring attribution for unlimited free calls. Located at [README line 1584](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1584).

- **CoinMarketCap API** – Cryptocurrency market data and fiat-to-crypto exchange rates with 10,000 calls per month. Located at [README line 1577](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1577).

### Fraud Detection and Security

- **FraudLabsPRO** – Payment fraud detection and chargeback prevention service offering 500 queries per month on the Micro plan. Located at [README line 1583](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1583).

### Usage-Based Billing and Monetization

- **Moesif API Monetization** – Usage-based billing platform with Stripe and Chargebee integration, offering 30,000 events per month. Located at [README line 1585](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1585).

### Dynamic Pricing and Tax Compliance

- **ParityVend** – Dynamic pricing based on visitor location using purchasing-power parity (PPP), offering 7,500 API requests per month. Located at [README line 1586](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1586).

- **vatlayer** – VAT number validation and EU VAT rates with 100 requests per month. Located at [README line 1589](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1589).

## How to Integrate These Billing APIs

The services listed in [`README.md`](https://github.com/ripienaar/free-for-dev/blob/main/README.md) lines 1576-1589 expose RESTful endpoints that accept standard HTTP requests. Below are practical `curl` examples for three representative services.

### Currency Conversion with Currencyapi

```bash
curl "https://api.currencyapi.com/v3/latest?apikey=YOUR_API_KEY&base_currency=USD&currencies=EUR,GBP"

```

The JSON response includes conversion rates for the requested target currencies:

```json
{
  "data": {
    "EUR": { "value": 0.91 },
    "GBP": { "value": 0.78 }
  }
}

```

### Fraud Detection with FraudLabsPRO

```bash
curl -X POST "https://api.fraudlabspro.com/v1/transaction" \
  -d "key=YOUR_API_KEY" \
  -d "card_number=4111111111111111" \
  -d "amount=49.99" \
  -d "currency=USD"

```

The API returns a risk assessment:

```json
{
  "is_fraud": false,
  "risk_score": 3,
  "message": "Low risk"
}

```

### Subscription Verification with RevenueCat

```bash
curl -H "Authorization: Bearer YOUR_API_KEY" \
     "https://api.revenuecat.com/v1/subscribers/USER_ID"

```

The response contains entitlement status and expiration dates:

```json
{
  "subscriber": {
    "entitlements": { "premium": { "expires_date": "2026-03-01T00:00:00Z" } },
    "first_seen": "2024-10-12T14:23:45Z"
  }
}

```

These examples illustrate the HTTP-first architecture of these free payment processing and billing APIs, making them straightforward to integrate into any backend stack including Node.js, Python, or Go.

## Navigating the Source Repository

The curated data resides in specific files within the `ripienaar/free-for-dev` GitHub repository. Understanding these locations helps you verify current limits and discover new additions.

- **[`README.md`](https://github.com/ripienaar/free-for-dev/blob/main/README.md)** – The primary source of truth containing the "Payment and Billing Integration" section between lines 1576 and 1589. This markdown file is the raw data behind all listings. [View on GitHub](https://github.com/ripienaar/free-for-dev/blob/master/README.md)

- **[`index.html`](https://github.com/ripienaar/free-for-dev/blob/main/index.html)** – A static site generator that renders the README content for web browsing. The payment section appears here in a searchable, formatted layout. [View on GitHub](https://github.com/ripienaar/free-for-dev/blob/master/index.html)

- **`CNAME`** – Configuration file for the custom domain `freefor.dev` that hosts the static site, providing easy access to the payment API listings. [View on GitHub](https://github.com/ripienaar/free-for-dev/blob/master/CNAME)

## Summary

The ripienaar/free-for-dev repository provides a comprehensive index of **free payment processing and billing APIs** suitable for startups and side projects. Key takeaways include:

- **Mobile subscriptions**: Adapty.io and Qonversion offer free tiers up to $10,000 in monthly revenue, while RevenueCat provides $2,500.
- **Currency conversion**: Eight different FX rate APIs provide between 100 and 10,000 free requests monthly, with Currencyapi and exchangerate-api.com offering the most generous web-tier limits.
- **Security and compliance**: FraudLabsPRO adds 500 monthly fraud checks, while vatlayer handles EU VAT validation.
- **Monetization infrastructure**: Moesif enables usage-based billing for 30,000 events per month, and ParityVend supports geographic pricing adjustments.

## Frequently Asked Questions

### What are the revenue limits for free mobile subscription APIs?

Adapty.io and Qonversion both offer free tiers supporting up to **$10,000** in monthly tracked revenue, making them suitable for early-stage apps with growing user bases. RevenueCat provides a lower threshold of **$2,500** per month but includes comprehensive cross-platform receipt validation and webhook processing capabilities.

### Can I use these payment APIs for production applications?

Yes, the free tiers listed in [`README.md`](https://github.com/ripienaar/free-for-dev/blob/main/README.md) lines 1576-1589 are designed for production use within their specified limits. Services like Moesif (30,000 events/month) and FraudLabsPRO (500 queries/month) provide sufficient capacity for small to medium applications, though you should implement usage monitoring to avoid hitting hard limits that could interrupt service.

### Which free API is best for multi-currency support?

For simple currency conversion, **Currencyapi** offers 300 requests per month with a straightforward JSON interface, while **exchangerate-api.com** provides 1,500 monthly requests with daily rate updates. If you need cryptocurrency data alongside fiat currencies, **CoinMarketCap API** offers 10,000 calls per month covering both asset types and exchange rates.

### How do I access the raw list of payment APIs?

The definitive list resides in the [`README.md`](https://github.com/ripienaar/free-for-dev/blob/main/README.md) file of the ripienaar/free-for-dev repository between lines 1576 and 1589. You can view the raw markdown on [GitHub](https://github.com/ripienaar/free-for-dev/blob/master/README.md#L1576) or browse the rendered version at the custom domain `freefor.dev`.