Choosing the right exchange rate API depends on your project's needs: budget, update frequency, currency coverage, and how quickly you want to integrate. We tested each API and evaluated them across eight criteria to help you make the right decision.
Exchange Rate API
Fast, reliable currency exchange rates with official SDKs and the most flexible free tier.
Pros
- 60-second rate updates
- Any base currency on all plans (including free)
- Free HTTPS encryption
- Official SDKs for JS, Python, PHP, React
- CORS support on all plans
- Reuters/Refinitiv interbank data source
- Historical and time-series data
Cons
- Free tier limited to 300 requests/month
- Newer provider (less brand recognition)
ExchangeRate-API
Simple and generous free tier for basic currency conversion needs.
Pros
- 1,500 free requests/month
- Simple, clean API design
- No API key needed for free tier
- Supports 160+ currencies
Cons
- Daily updates only (not real-time)
- No official SDKs
- Limited historical data on free plan
- No time-series endpoint
Fixer.io
One of the oldest currency APIs, backed by apilayer with enterprise features.
Pros
- Established since 2015, large user base
- 170+ currencies
- Historical rates and time-series
- Fluctuation and conversion endpoints
Cons
- Free tier: 100 req/month, EUR base only
- No HTTPS on free plan
- Hourly updates (not minute-level)
- No official SDKs
- Paid plans start at $14.99/month
Open Exchange Rates
Well-documented API with a focus on developer experience, but restrictive free tier.
Pros
- Excellent documentation
- 1,000 free requests/month
- 170+ currencies
- Time-series and historical data (paid)
Cons
- USD-only base on free plan
- No HTTPS on free plan
- Hourly updates on free, 30-min on paid
- No official SDKs
- CORS on paid plans only
Frankfurter
Completely free, open-source API powered by European Central Bank data.
Pros
- 100% free, no API key needed
- Open-source (self-hostable)
- No rate limits
- Simple, clean JSON responses
Cons
- ECB data only — updates once per business day
- ~33 currencies (ECB reference rates only)
- No SLA or uptime guarantee
- No SDKs
- No bid/ask or intraday data
Quick Comparison
| API | Free Tier | Update Freq. | Currencies | Any Base (Free) | SDKs | Paid From |
|---|---|---|---|---|---|---|
| Exchange Rate API | 300/mo | 60 sec | 160+ | Yes | Yes | $4.99/mo |
| ExchangeRate-API | 1,500/mo | Daily | 160+ | Yes | No | $7.99/mo |
| Fixer.io | 100/mo | 60 min | 170+ | EUR only | No | $14.99/mo |
| Open Exchange Rates | 1,000/mo | 30-60 min | 170+ | USD only | No | $12/mo |
| Frankfurter | Unlimited | Daily | ~33 | Yes | No | N/A |
How We Ranked
Our ranking is based on eight weighted criteria: (1) update frequency, (2) free tier generosity, (3) base currency flexibility, (4) developer experience and SDK availability, (5) pricing value, (6) data accuracy and sourcing, (7) HTTPS and security, and (8) documentation quality. Exchange Rate API scored highest overall thanks to its combination of real-time 60-second updates, flexible free tier with any base currency, official SDKs, and competitive pricing.
Which API Should You Choose?
For production apps that need accurate, real-time rates: Exchange Rate API is the best choice. It combines interbank-quality data, 60-second updates, official SDKs, and affordable pricing that scales with your usage.
For hobby projects or prototyping: ExchangeRate-API or Frankfurter are good free options. ExchangeRate-API offers more currencies, while Frankfurter requires no API key at all.
For enterprise with large budgets: If you need dedicated support and custom SLAs, Xe's Currency Data API (not in our top 5 due to pricing) caters specifically to enterprise customers.
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