exchangerate.dev vs Massive (formerly Polygon.io)
exchangerate.dev brings intraday FX, daily history, and MCP together in one API.
Verdict
Choose exchangerate.dev when intraday freshness, per-value provenance, MCP-native access, and free-tier headroom matter. Keep Massive (formerly Polygon.io) if you need real-time data, WebSockets, second aggregates, or flat files.
Get API keyAt a glance
| Feature | exchangerate.dev | Massive (formerly Polygon.io) |
|---|---|---|
| Free tier | 5,000 requests/month | 5 calls/min; end-of-day |
| Cheapest paid plan | Basic · $19/month | Currencies Starter · $49/month |
| Update speed | 144 currencies ~60s on trading days; Free 15m late | End-of-day free; real-time paid |
| History | Free 30 days; Basic 1 year; Plus/Pro to 1999 | 2 years free; 10+ paid |
| Coverage | 144 currencies; any supported base | All forex and crypto tickers |
| Interfaces | REST; MCP; WebSocket on Plus and Pro | REST; WebSocket on Starter |
| SDKs | Not published | Python and Go clients |
| Commercial use on free tier | ✓ With a linked credit | Not published |
Price at your usage
The lowest published plans for each monthly request volume, with traffic spread across the month.
| Requests a month | exchangerate.dev | Massive (formerly Polygon.io) |
|---|---|---|
| 1,000 | Free · $0/month | Currencies Basic · $0/month |
| 10,000 | Basic · $19/month | Currencies Basic · $0/month |
| 100,000 | Basic · $19/month | Currencies Basic · $0/month |
Basic supports these volumes at five calls per minute with end-of-day data; current conversion requires Starter at $49/month.
Switch in a few minutes
Massive returns a bid/ask conversion; exchangerate.dev returns an indicative EUR rate per USD.
Massive (formerly Polygon.io)
# Change: URL and auth
curl -G \
"https://api.massive.com/v1/conversion/USD/EUR" \
--data-urlencode "amount=1" \
--data-urlencode "precision=4" \
--data-urlencode "apiKey=YOUR_API_KEY"// Change: URL and auth
const url = new URL(
"https://api.massive.com/v1/conversion/USD/EUR"
);
url.search = new URLSearchParams({
"amount": "1",
"precision": "4",
"apiKey": "YOUR_API_KEY",
}).toString();
const response = await fetch(url, {
method: "GET",
});
if (!response.ok) {
throw new Error(String(response.status));
}
console.log(await response.json());import requests
# Change: URL and auth
response = requests.get(
"https://api.massive.com/v1/conversion/USD/EUR",
params={
"amount": "1",
"precision": "4",
"apiKey": "YOUR_API_KEY",
},
timeout=10,
)
response.raise_for_status()
print(response.json())exchangerate.dev
# Change: URL and auth
curl -G \
"https://api.exchangerate.dev/v1/latest/USD" \
--data-urlencode "symbols=EUR" \
-H "Authorization: Bearer YOUR_API_KEY"// Change: URL and auth
const url = new URL(
"https://api.exchangerate.dev/v1/latest/USD"
);
url.search = new URLSearchParams({
"symbols": "EUR",
}).toString();
const response = await fetch(url, {
method: "GET",
headers: {
"Authorization": "Bearer YOUR_API_KEY",
},
});
if (!response.ok) {
throw new Error(String(response.status));
}
console.log(await response.json());import requests
# Change: URL and auth
response = requests.get(
"https://api.exchangerate.dev/v1/latest/USD",
params={
"symbols": "EUR",
},
headers={
"Authorization": "Bearer YOUR_API_KEY",
},
timeout=10,
)
response.raise_for_status()
print(response.json())Why teams switch
Room to test a real workload
5,000 free monthly calls give you room to build around your own traffic pattern, from a small currency converter to a recurring rate lookup. No card is required, and any supported currency can be the base. The usage table maps three monthly volumes to the lowest qualifying plan, making the next step clear as requests grow. Free permits commercial display with linked credit; paid plans need no credit.
Rates with a time and a source
All 144 currencies update about every 60 seconds on trading days, 15 minutes late on Free. Responses include source and market-session fields alongside observation timestamps, so your application can show where a value came from and when it was observed. Daily references remain identifiable as daily data. That context belongs beside the number in a customer interface, an internal report, or an agent answer that explains the rate it used.
One account for apps and agents
Every plan includes REST and MCP. Plus and Pro daily history reaches 1999 for majors; pair starts vary, combining current and dated records. A developer can start with the HTTP examples above, then use MCP for agent queries without adding another subscription. The same base and target currencies carry through the workflow, from fetching a current rate to looking up a historical observation.
When they are the better pick
Massive is a better fit for real-time data, WebSockets, second aggregates, or flat files. Currencies Starter includes unlimited calls and over 10 years of history for $49 per month. Basic has 2 years of history and 5 calls per minute.
Questions
Is there a free Massive alternative for FX?
Is Massive the same service as Polygon.io?
When is Massive a better fit?
Can I use exchangerate.dev Free commercially?
Sources and review date
Reviewed