exchangerate.dev vs Massive (formerly Polygon.io)

exchangerate.dev brings intraday FX, daily history, and MCP together in one API.

exchangerate.devReviewed October 2026

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 key

At a glance

Featureexchangerate.devMassive (formerly Polygon.io)
Free tier5,000 requests/month5 calls/min; end-of-day
Cheapest paid planBasic · $19/monthCurrencies Starter · $49/month
Update speed144 currencies ~60s on trading days; Free 15m lateEnd-of-day free; real-time paid
HistoryFree 30 days; Basic 1 year; Plus/Pro to 19992 years free; 10+ paid
Coverage144 currencies; any supported baseAll forex and crypto tickers
InterfacesREST; MCP; WebSocket on Plus and ProREST; WebSocket on Starter
SDKsNot publishedPython and Go clients
Commercial use on free tier✓ With a linked creditNot published

Price at your usage

The lowest published plans for each monthly request volume, with traffic spread across the month.

Requests a monthexchangerate.devMassive (formerly Polygon.io)
1,000Free · $0/monthCurrencies Basic · $0/month
10,000Basic · $19/monthCurrencies Basic · $0/month
100,000Basic · $19/monthCurrencies 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"

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"

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?
Yes. exchangerate.dev includes 5,000 calls per month and updates for all 144 currencies about every 60 seconds on trading days, 15 minutes late on Free. Massive Currencies Basic is free, with 5 calls per minute, end-of-day data, and 2 years of history.
Is Massive the same service as Polygon.io?
Polygon.io has rebranded as Massive. The former Polygon.io pricing page redirects to Massive pricing. This comparison covers its currencies plans.
When is Massive a better fit?
Choose Massive Currencies Starter for real-time data, WebSockets, second aggregates, or flat files. It costs $49 per month with unlimited calls and over 10 years of history. Basic does not include WebSockets.
Can I use exchangerate.dev Free commercially?
Free: commercial display with visible linked credit near rates. Basic: no credit required, $19/month.

Sources and review date

Reviewed