Best interest rate and yield curve APIs in 2026

Narwhal API provides five national yield curves through one schema. FRED and US Treasury offer free US series. ECB Data Portal covers euro-area curves. Curve methods differ, and Narwhal does not offer policy-rate series.

Decision

Choose Narwhal for five countries through REST and MCP. Choose FRED for US rates and revision vintages, Treasury for direct US par curves, or ECB for euro-area curves. Choose Trading Economics for forecasts and a calendar.

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Provider shortlist

Curves use different methods and publishing schedules. Narwhal API is owned and operated by Nusantara Ventures, LLC.

US Treasury

Direct US Treasury par yield curves

Compare the options

Best fit is not feature parity. Check the evidence and limitation together.

ProviderBest forEvidence checkedImportant limitation
Narwhal APIFive national yield curves in one schemaUS, UK, Germany, Japan and Canada curves include latest, source-date and paginated history access through REST and MCP.No policy-rate series. Canada publishes about weekly with a 2 to 3 week lag.
FREDFree US rates and revision vintagesDGS10 provides daily Treasury constant-maturity yields; DFF provides the daily federal funds effective rate. ALFRED provides revision vintages.Series are accessed individually. Commercial use has additional restrictions, and some series require separate copyright permission.
US TreasuryDirect US Treasury par yield curvesDaily par yield curves are available through XML and CSV from 1990, with 14 maturities from 1 month to 30 years.This is a US par curve. Treasury changed feed addresses, so integrations using old URLs can break.
ECB Data PortalDaily euro-area yield curvesSDMX REST provides daily curves for AAA-rated and all euro-area central government bonds, with residual maturities from 3 months to 30 years.Euro area only. The page specifies public information use, not pricing quotations. Reuse requires citing the ECB and stating changes.
Trading EconomicsRates research alongside forecasts and calendarsIndicators, calendars, markets and forecasts cover 196 countries. Standard costs $199 a month for 500 requests.Standard is limited to one user. There is no ongoing free tier.
Financial Modeling PrepTreasury rates alongside indicators and a calendarEconomics endpoints cover Treasury rates from 1 month to 30 years, indicators by name and an economic calendar. An official MCP server is available.Free Basic is for personal use. Displaying or redistributing data needs a separate agreement.
Alpha VantageUS economic indicators through an official MCP serverEconomic coverage includes Treasury yield, the federal funds rate, GDP, CPI, unemployment and nonfarm payroll. Free access allows 25 requests a day.Economic indicators are US only. Paid plans start at $49.99 a month.

Choose by requirement

Match the curve method

Narwhal shares a schema across five national curves. US par yields, UK and Canadian zero-coupon curves, German spot rates and Japanese constant-maturity yields measure different things.

Separate yields from policy rates

Narwhal offers national yield curves without policy-rate series. FRED includes the federal funds effective rate as DFF, alongside Treasury yield series such as DGS10.

Check publication schedules

Narwhal checks most curve sources daily and Canada weekly. Canada's curve has a 2 to 3 week publication lag. ECB publication can slip a day.

Sources and review date

Each detailed provider page lists the first-party documentation used, its evidence boundaries, and its review date.

Reviewed:

Test the overlapping job

Inspect Narwhal's published coverage and response contract before choosing a provider.

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