Does Frankfurter or ExchangeRate-API update faster?

Neither updates intraday. Frankfurter publishes once per business day around 16:00 CET, tied to the ECB reference fix, with nothing published on weekends. ExchangeRate-API's open-access endpoint also updates once a day. If you need a rate that moves through the trading day, neither of these covers it.

Do I have to display attribution for Frankfurter the way I do for ExchangeRate-API?

No. Frankfurter carries no stated attribution requirement — it is an open-source project. ExchangeRate-API's open-access terms specifically require displaying "Rates By Exchange Rate API" with a link back to exchangerate-api.com wherever the data appears.

Can I redistribute the data from either one?

ExchangeRate-API explicitly prohibits redistributing its raw data via open access, though caching it for your own application is fine. Frankfurter, as an open-source project without that clause stated, is the more permissive choice if repackaging or republishing the feed is part of your plan.

What happens if I exceed the free limit on either one?

ExchangeRate-API's open access returns an HTTP 429 once you exceed its rate limit, and the restriction clears after 20 minutes. Frankfurter states no enforced quota, so there is no documented equivalent penalty — but "no enforced quota" is not the same guarantee as a published SLA.

Is there a paid or keyed tier for either of these free options?

ExchangeRate-API does: a keyed free tier above open access gives 1,500 requests a month without the attribution requirement, and paid tiers exist above that. Frankfurter has no keyed tier — the open, no-key API is the entire product.

Which one should I pick if I have not decided what the project needs yet?

Frankfurter, on the grounds that it costs nothing, needs no key, and imposes no attribution string you would later have to remove. If the project turns out to need a keyed upgrade path or you find the attribution acceptable, moving to ExchangeRate-API later is a base-URL change and a response-shape check, not a rewrite.

Comparison/Comparison

Frankfurter vs ExchangeRate-API: the two free, no-key options compared

Both let you make a request right now with no signup and no key. Past that, they diverge: one is open-source ECB data with no quota, the other is a commercial API giving away a limited, attributed slice of its feed. Neither is wrong. They fit different jobs.

ERexchangerate.dev·Aug 1, 2026·6 min read

Frankfurter has no quota at all but publishes once a day, only on business days, from the European Central Bank. ExchangeRate-API's open access also needs no key, updates once a day too, but comes with an attribution requirement and a ban on redistributing the raw data. Pick by what your project does with the data, not by which name is more familiar.

Key points

Frankfurter: open-source, no key, no enforced quota, ECB reference rates only — once a day, business days only, nothing on weekends.

ExchangeRate-API open access: no key needed either, but updates once daily, requires visible attribution, and prohibits redistributing the data.

Frankfurter has no rate-limit penalty by design; ExchangeRate-API's open endpoint returns HTTP 429 if you exceed its limit, clearing after 20 minutes.

ExchangeRate-API has a keyed tier (1,500 requests/month) if you outgrow open access without wanting attribution; Frankfurter has no keyed tier at all.

Neither source updates intraday. Both are a single daily snapshot, just on different licensing terms.

Limits and terms above were checked directly against each vendor in August 2026 — verify before locking in a dependency.

What both get you, for nothing

Type a curl command against either service right now and you get JSON back. No signup form, no key generation step, no credit card — rarer than it should be in this space, and why both show up on every "free FX API" list.

Past that first request, they stop resembling each other. Frankfurter is a standalone open-source project publishing European Central Bank reference rates. ExchangeRate-API is a commercial product with paid tiers, and open.er-api.com is the free, unauthenticated slice of that product — a funnel, roomier than usual because the company sells the keyed tiers above it.

Frankfurter: no key, no quota, ECB only

Frankfurter wraps ECB reference rates in a clean JSON API. There is no API key at any tier, and no enforced request quota — the project does not meter you. It is open source, so the code is inspectable before pointing production traffic at it.

The constraint is the underlying data, not the API wrapper. ECB reference rates publish once per business day, at roughly 16:00 CET, with nothing published at all on Saturday or Sunday — request a weekend date and you get the prior Friday's fix, because the ECB itself did not publish one.

ExchangeRate-API: no key, one attribution string, one restriction

The open-access endpoint at open.er-api.com needs no API key either — call it the same way you'd call Frankfurter, cold, no setup. It updates once a day, same cadence as Frankfurter, though not ECB-sourced.

Two conditions come with it: attribution, displaying "Rates By Exchange Rate API" with a link back to exchangerate-api.com, and no redistribution — you cannot republish the raw feed, though caching for your own app is allowed. Exceed the rate limit and you get an HTTP 429; the block lifts after 20 minutes. A keyed plan without the attribution requirement gives 1,500 requests a month.

Side by side

FrankfurterExchangeRate-API (open access)

API key requiredNoNo

Update frequencyOnce/business day (~16:00 CET)Once/day

Weekend dataNone — ECB publishes nothingNot specified as ECB-tied; still one fix/day

Enforced quotaNoneRate-limited; 429 clears after 20 min

Attribution requiredNoYes — visible link back required

RedistributionOpen source, no restriction statedProhibited; caching allowed

Upgrade pathNone — no keyed tier existsKeyed tier, 1,500 req/month

bash · each rival's own open endpointcopy

# Frankfurter — no key, ECB reference rates
curl "https://api.frankfurter.dev/v1/latest?from=USD&to=EUR,GBP"

# ExchangeRate-API — open access, no key, attribution required in your UI
curl "https://open.er-api.com/v6/latest/USD"

Which one for which job

An internal dashboard has no attribution surface to satisfy anyway, so ExchangeRate-API's condition is moot and either source works. Pick based on whether you want to inspect the code (Frankfurter) or want a keyed upgrade path ready if traffic grows (ExchangeRate-API).

If the surface is public — a currency converter, a price widget on a product page — the attribution line starts to matter. Frankfurter carries no such obligation. Where a visible attribution link is a non-issue for your product, ExchangeRate-API's open access is just as usable.

Read the fine print before pointing a high-volume cron job at either one. Frankfurter states no enforced quota, which sounds unlimited but is not a documented SLA. ExchangeRate-API is explicit about its ceiling — hit the limit, get a 429, wait 20 minutes.

Weekends expose the ECB-only sourcing most plainly. Picture a Saturday travel-booking flow that needs a rate rendered, not a five-day-old placeholder — no ECB fix means no fresh number, any day the market is closed in Frankfurt.

Both are daily snapshots, not live feeds

Neither source updates through the trading day. Both are actually "this morning's rate, or Friday's if it's the weekend" — a different guarantee from an intraday feed, worth confirming before either goes into production.

If neither fits

Both are once-a-day snapshots by design, and for a large share of FX use cases — invoicing, accounting exports, a weekly report — that is the right amount of freshness. If your project needs a rate that reflects what changed an hour ago, that is a different category of source, and exchangerate.dev is one option: a keyed API with a live-updating source on major pairs. It is not a substitute for either on their own terms — it is the option once intraday freshness becomes the actual requirement.

exchangerate.dev

Independent comparisons of FX data providers, checked against each vendor's own docs.