Migrate from Fixer

Fixer is a commercial FX API with a familiar latest and convert shape. Most of the integration survives a move to CurrencyCore because the ISO codes and the “units per one unit of base” arithmetic stay the same. The auth model, the default base, the history packaging, and the error envelope do not.

Public Fixer pricing and coverage below were checked on 2026-11-10. Verify the vendor’s current plan before you budget.

What changes at a glance

CurrencyCore does not sell a 60-second executable quote. If the Pro Plus cadence is a product requirement, Fixer remains the better fit. CurrencyCore is for reference rates, longer history, PPP, and analytics.

1. Replace access_key with a bearer token

Fixer samples pass the key in the query string:

curl "https://data.fixer.io/api/latest?access_key=YOUR_KEY&base=USD&symbols=EUR,INR"

CurrencyCore uses a header:

curl "https://api.currency-core.com/v1/rates/USD" \
  -H "Authorization: Bearer cc_live_your_key"

Remove access_key from URLs, logs, fixtures, and browser history. Do not keep query-string auth as a fallback in staging: dual auth doubles the places a key can leak. Use a test key on Free while integrating, then a live key on a paid plan. See Authentication.

2. Map endpoints

The Fixer symbols filter has no direct CurrencyCore parameter. /v1/rates/USD returns the full snapshot; read the codes you need from rates and cache the response. That trades a larger payload for one fewer per-call parameter.

3. Map response fields

A Fixer latest response looks like this:

{
  "success": true,
  "timestamp": 1762732800,
  "base": "EUR",
  "date": "2026-11-10",
  "rates": { "USD": 1.0861, "INR": 91.62 }
}

The CurrencyCore equivalent for the same base is:

{
  "base": "EUR",
  "date": "2026-11-10",
  "rates": { "EUR": 1, "USD": 1.0861, "INR": 91.62 }
}

base, date, and rates map directly. The success flag has no equivalent: CurrencyCore returns HTTP 200 on success and an HTTP status plus an error envelope on failure. Read the status first, then error.code if present.

A Fixer conversion:

{ "success": true, "result": 108.61 }

becomes:

{ "from": "USD", "amount": 100, "date": "2026-11-10", "results": [{ "to": "INR", "result": 9162, "rate": 91.62 }] }

The converted amount is results[0].result. The rate is results[0].rate. If you send several targets, match by results[].to.

A Fixer timeseries keyed by date:

{ "success": true, "start_date": "2026-11-09", "end_date": "2026-11-10", "rates": { "2026-11-09": { "INR": 91.5 }, "2026-11-10": { "INR": 91.62 } } }

becomes a dense CurrencyCore series:

{ "currency": "INR", "base": "USD", "from": "2026-11-09", "to": "2026-11-10", "rates": { "2026-11-09": 91.5, "2026-11-10": 91.62 } }

CurrencyCore includes weekends and holidays by carrying the previous rate forward. Provider series that omit non-trading days need a filter in your adapter if your chart depends on gaps.

See Errors for status codes and retry behavior.

4. Plan for the coverage differences

Fixer advertises 170 currencies and history from 1999. CurrencyCore advertises 160 fiat currencies, with deeper history on a narrower set of pairs. The practical checks:

• Run a code diff between your Fixer usage and /v1/currencies. Do not assume every Fixer code is quoted by CurrencyCore.
• CurrencyCore does not quote metals or crypto. If your Fixer usage includes those instruments, keep a separate provider.
• Free is limited to the last 30 days of history even though the dataset reaches 1949. Starter and above get full history.
• “History from 1949” is not a promise of daily data for every pair. It is annual parity for GBP/USD and USD/INR, daily majors from 1971, and EUR pairs from 1999. See History coverage and the /history reference.

Fixer’s Basic plan is $14.99/mo for 10,000 calls and hourly updates, with 60-second updates on Pro Plus. CurrencyCore starts at $9/mo for 50,000 requests and full history, but it does not offer a 60-second cadence. Compare the plan features you actually need rather than the headline request count.

5. Cut over

1. Create a CurrencyCore organization and a test key.
2. Replace access_key with the bearer header in one client module.
3. Rewrite /latest calls as /v1/rates/{base} and delete the symbols parameter in favor of local filtering.
4. Rewrite /convert calls and read results[0].
5. Rewrite /timeseries calls as /v1/history, one currency at a time.
6. Shadow a sample of production requests and compare the same fixing dates.
7. Switch reads, watch 401, 403, and 429, then revoke the Fixer key.
8. Keep the old adapter until the next billing cycle in case rollback is needed.

For the provider-neutral version of this checklist, see Migrate an existing integration.

Related

• Migration overview
• OpenAPI specification
• Authentication
• Errors
• Rate limits
• All integration guides
• /rates endpoint
• /convert endpoint
• /history endpoint