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

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 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.

• 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.

• 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.

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.

• exchangerate-api.com – Easy-to-use JSON conversion API with 1,500 requests per month and daily updates. Located at README line 1582.

• currencylayer – Reliable exchange rate service providing 100 requests per month. Located at README line 1581.

• 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.

• CurrencyFreaks – Current and historical exchange rates with 1,000 requests per month on the Developer plan. Located at README line 1580.

• FxRatesAPI – Real-time and historical FX rates requiring attribution for unlimited free calls. Located at README line 1584.

• CoinMarketCap API – Cryptocurrency market data and fiat-to-crypto exchange rates with 10,000 calls per month. Located at README line 1577.

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.

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.

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.

• vatlayer – VAT number validation and EU VAT rates with 100 requests per month. Located at README line 1589.

How to Integrate These Billing APIs

The services listed in 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

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:

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

Fraud Detection with FraudLabsPRO

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:

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

Subscription Verification with RevenueCat

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

The response contains entitlement status and expiration dates:

{
  "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 – 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

• 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

• 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

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 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 file of the ripienaar/free-for-dev repository between lines 1576 and 1589. You can view the raw markdown on GitHub or browse the rendered version at the custom domain freefor.dev.

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