Data Sources: Open Exchange Rates' Blended Feed vs AllRatesToday's Reuters + Interbank

When your product touches money, "where does the rate come from?" is a question your risk, compliance, or audit team will eventually ask. If the answer is vague, the conversation gets expensive.

Open Exchange Rates describes its data as: "collected from several reliable sources and blended together algorithmically... other sources are not currently disclosed, but providers are monitored closely and routinely checked." That's a reasonable description for a consumer-facing product. For a regulated environment, it leaves gaps.

AllRatesToday publishes its sources explicitly: Reuters (Refinitiv) and interbank market feeds. This article explains why that transparency matters, what the practical accuracy difference looks like, and when it actually affects your decision.

The two approaches

Open Exchange Rates: blended, undisclosed

From their FAQ and documentation:

• Data is aggregated from multiple sources.
• The specific providers are not disclosed publicly.
• Providers are monitored internally.
• Rates aim to be "consistent and unbiased, providing the most representative market rate possible — generally the midpoint between the most common buy/sell prices."
• They note rates "are accurate enough for 99% of cases (shopping carts, personal finance, estimates, etc.)."

For most web apps, this is fine. For a regulated fintech or a public company's accounting close, the audit trail stops at "a blend."

AllRatesToday: named, publicly disclosed

Sources:

• Reuters (Refinitiv) — the institutional FX data feed used by banks, asset managers, and trading desks.
• Interbank market feeds — the rates at which banks transact with each other.

Same mid-market rate philosophy: no bank markup, no retail spread, just the midpoint between buy and sell in the institutional market.

Why sourcing transparency matters

Compliance and audit

• SOX (US public companies): auditors ask how revenue denominated in foreign currencies was translated. "Blended from undisclosed sources" is a weak answer.
• IFRS / GAAP reporting: exchange rate disclosures in financial statements often require naming the source.
• SOC 2 / ISO 27001: service organization controls ask about data provenance for inputs to pricing and billing.
• FX-regulated industries (remittance, payments, broker-dealer): regulators care whether your rate source is reproducible and independently verifiable.

Reuters/Refinitiv and interbank are named, industry-standard feeds. Easy to describe in an audit memo, easy to reproduce if someone asks.

Accuracy under stress

Blended feeds average out discrepancies between sources. That can be good (no single outlier dominates) or bad (a real move gets smoothed before it propagates). Reuters/Refinitiv publishes continuous intraday quotes sampled from actual interbank transactions, so the feed reflects real market activity, not a cleaned-up mid-market synthesis.

In calm markets, the two approaches produce nearly identical numbers. In volatile markets — central bank announcements, macro surprises, geopolitical events — the Reuters/interbank feed tends to move first and more sharply.

Reproducibility

If a customer disputes a rate ("you charged me at 0.923 but the market was at 0.925 at that time"), you need to point them at a source they can verify. A named feed makes that trivial; a blended feed makes it a judgment call.

When the difference doesn't matter

• Price display for informational purposes ("USD/EUR is roughly 0.92 today").
• Shopping carts where rates are hedged through a payment processor (the processor's rate is what actually applies).
• Analytics dashboards where accuracy to within 5-10 basis points is fine.
• Non-regulated use cases where no one will ever ask for source documentation.

When the difference matters

• Anywhere the rate is the contractual conversion rate (remittance, cross-border invoicing, settlement).
• Audited financial reporting.
• Regulated industries (fintech, broker-dealer, payments).
• Backtests where you want the most realistic intraday behavior.
• Any case where a customer or auditor could demand source documentation.

The data-pipeline picture

OpenExchangeRates (inferred from public descriptions)

[Undisclosed Source A] ──┐
[Undisclosed Source B] ──┤
[Undisclosed Source C] ──┼──> Blending algorithm ──> latest.json (updated hourly)
[Undisclosed Source N] ──┘

Opacity: which sources, how many, what weights, what rejection rules.

AllRatesToday

Reuters (Refinitiv) FX feed ──┐
Interbank market feeds ───────┼──> Mid-market aggregation ──> /api/v1/rates (updated every 60s)

Transparency: sources named, philosophy stated (mid-market), cadence documented.

How to evaluate your own situation

Ask these questions about your use case:

1. Will anyone ever ask where this rate came from? (Auditor, regulator, customer, internal finance team.)
2. Is the rate the contractual amount? (Vs. a display-only reference.)
3. Does my industry have rules about FX data provenance? (Payments, remittance, insurance, broker-dealer.)
4. Do I need the freshest possible rate during volatile sessions? (Trading-adjacent, treasury, hedging.)

One "yes" = sourcing transparency matters enough to choose a named-feed provider. No "yes"es = blended is fine.

The practical test

Run both providers side-by-side for a month and log the delta on major pairs during volatile days (US CPI release, ECB meeting, BoJ intervention). You'll see:

• Calm day: delta <5 bps most of the time.
• Volatile hour: delta can reach 20-50 bps as OpenExchangeRates' hourly cadence lags the Reuters/interbank feed.

For most apps, 5 bps on a calm day doesn't matter. For any app where the rate is the contractual amount, a 30-bp gap during volatility does.