- Exchange rate APIs at a glance
- Eleven exchange rate APIs to compare
- Where to start for your project
- What central bank reference rates are for
- Daily reference rates versus live market rates
- Questions to ask before you choose an exchange rate API
- Signs you need an exchange rate API
- My plain advice on choosing a currency exchange API
- Frequently asked questions
The best currency exchange APIs send live and historical exchange rates to your website, app or finance system automatically, so conversions are always up to date. Some are free services built on central bank data, while others come from established forex companies. Eleven options follow in no particular order.
Selling to customers abroad, paying overseas suppliers or reporting in more than one currency all depend on one small number: today's exchange rate. Typing it in by hand works for a week, then someone forgets and the totals drift.
The eleven APIs below are listed alphabetically and in no particular order, and every description comes from the provider's own website, read this week. If you're selling internationally, my guide on how to globalise and localise your ecommerce website covers the bigger picture.
Exchange rate APIs at a glance
I checked the free plan column on each tool's own website, as of Oct 2026. Yes means the site names a free plan, a free version, a free tier or an open source version. Trial only means a time-limited trial. Not stated means the pages I read named neither, even where there's a button inviting you to start for free, so check the vendor's page before you sign up.
| Tool | Type | Good for | Free plan |
|---|---|---|---|
| CurrencyAPI | Live and historical exchange rate API | Rates for online shops and SaaS | Yes |
| CurrencyBeacon | REST currency API with code samples | Code samples and AI agent access | Not stated |
| CurrencyFreaks | Real-time exchange rate API | Real-time rates on a free plan | Yes |
| currencylayer | Exchange rate and forex API | Forex rates for business apps | Yes |
| ExchangeRate-API | Free and pro currency converter API | A free key with no card | Yes |
| exchangeratesapi.io | Real-time and historical exchange rate API | Historical rates for reporting | Yes |
| Fixer | Lightweight forex rates and conversion API | A light JSON rates feed | Not stated |
| Frankfurter | Free open source exchange rates API | Central bank data with no key | Yes |
| OANDA Exchange Rates API | Forex rates API from OANDA | Rates from a long-standing forex name | Trial only |
| Open Exchange Rates | Currency data API for startups and brands | Startups with many open source libraries | Not stated |
| Xe Currency Data API | Currency converter and exchange rate API | A trusted converter brand for business | Trial only |
Eleven exchange rate APIs to compare
CurrencyAPI
Best for: Online businesses that want live and historical rates in one simple API, starting on a free account.
CurrencyBeacon
Best for: Developers who want a REST rates API with ready-made code samples and a server that AI tools can connect to.
CurrencyFreaks
Best for: Small projects that want real-time exchange rates and conversion over a secure connection, including on the free plan.
currencylayer
Best for: Business apps that want reliable exchange rates and conversion, with a free plan before moving to advanced access.
ExchangeRate-API
Best for: Developers who want a quick free key for exchange rates with no card details, and room to upgrade later.
exchangeratesapi.io
Best for: Finance and reporting tools that need real-time and historical exchange rates, with a free monthly allowance to test.
Fixer
Best for: Coders who want a simple, lightweight JSON API for current and historical foreign exchange rates.
Frankfurter
Best for: Builders who want free exchange rates drawn from central banks, with no API key and the option to self-host.
OANDA Exchange Rates API
Best for: Finance teams who want exchange rate data from an established forex company, with a short free trial to test it.
Open Exchange Rates
Best for: Startups that want consistent exchange rate data with plenty of community-built open source libraries to plug it in.
Xe Currency Data API
Best for: Larger businesses that want exchange rates from a household-name converter, connected to their finance and ERP systems.
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Where to start for your project
- Free central bank data with no key: Frankfurter.
- A free key with no card details: ExchangeRate-API.
- Historical rates for reporting: exchangeratesapi.io.
- A household-name converter for business systems: Xe Currency Data API.
- Code samples and AI agent access: CurrencyBeacon.
What central bank reference rates are for
The European Central Bank says its reference rates are usually updated at around 16:00 CET every working day, are published for information purposes only, and that using them for transactions is strongly discouraged.
That's worth knowing because many free APIs draw on central bank data. It's fine for showing a rough conversion on a product page, but checkout totals, invoices and your accounts should use the rate your payment provider or bank applies.
Daily reference rates versus live market rates
Daily reference rates are published once a working day. They're simple, stable and good enough for display conversions, reports and many small business tools.
Live market rates update through the day. They matter for trading, treasury work and any system where a small movement changes what you charge or receive, so check how often each provider updates.
Questions to ask before you choose an exchange rate API
- How often do the rates update?
- Where does the data come from?
- How far back does the historical data go?
- Which currencies does it cover, including smaller ones?
- Can I convert between any two currencies directly?
- Is the free allowance enough for my traffic?
Signs you need an exchange rate API
- Someone types rates into a spreadsheet. Automate it.
- Overseas customers ask what they'll pay. Show a conversion.
- Reports mix currencies. Convert with one source.
- Rates on your site are out of date. Pull them daily.
Do you make an exchange rate or currency data API? Tool makers can ask to be considered for a featured place on this list.
My plain advice on choosing a currency exchange API
Decide what the rate is for before you compare providers. A rough conversion on a product page and the rate on an invoice are different jobs, and mixing them up is how small, confusing differences end up in your accounts.
Cache rates rather than calling the API on every page view, and show customers which rate and time you used. If you're expanding abroad, my article on ways to maximise international reach has more ideas.
Frequently asked questions
What is a currency exchange API?
A currency exchange API is a service that sends exchange rates to your software automatically, so it can convert amounts between currencies.
Are there free currency exchange APIs?
Yes. Several providers offer free plans or free allowances, and some are free and open source. The free plan column above shows what each provider's own site says.
Can I use central bank rates for payments?
The European Central Bank says its reference rates are for information purposes only and strongly discourages using them for transactions.
How often do exchange rate APIs update?
It varies. Some update once a working day, while others update many times an hour on higher plans.
Do exchange rate APIs include historical rates?
Many do, which is useful for reports, accounting and checking past transactions.
Should I show customers converted amounts?
It can help international shoppers, but make it clear the conversion is approximate and the final amount depends on their card or bank.
