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Migration Guide — CurrencyLayer → fastFOREX API

Migrate from CurrencyLayer in under an hour

The main difference is CurrencyLayer's concatenated pair keys ("USDEUR") versus our plain currency keys ("EUR"). One small parsing change, a new base URL, and you're done. This guide maps every endpoint.

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Draft guide — endpoint mapping to be validated against both APIs' current docs before publishing.

Four steps, most of them small.

  1. Get a free API key

    7-day trial, no credit card, full plan access from minute one.

  2. Swap base URL & auth

    api.currencylayer.com → api.fastforex.io, and ?access_key= becomes the X-API-Key header.

  3. Simplify your keys

    Their quotes are keyed "USDEUR"; ours are keyed "EUR". Delete the source-prefix stripping you probably wrote.

  4. Benchmark, then cut over

    Run both in parallel on the trial, compare values and latency, switch when convinced.

Endpoint mapping

Every endpoint, translated.

One row per call your code makes today. Parameters keep their meaning — only names and paths change.

Purpose

CurrencyLayer

fastFOREX API

Live rates (specific currencies)

GET /live?currencies=EUR,GBP&source=USD

GET /fetch-multi?from=USD&to=EUR,GBP

Live rates (all currencies)

GET /live

GET /fetch-all?from=USD

Convert an amount

GET /convert?from=USD&to=EUR&amount=100

GET /convert?from=USD&to=EUR&amount=100 (identical!)

Historical (single date)

GET /historical?date=2020-01-01

GET /historical?date=2020-01-01 (identical!)

Time-frame (date range)

GET /timeframe?start_date=…&end_date=… ($59.99+)

GET /time-series?start=…&end=… (every plan)

Change / fluctuation

GET /change ($99.99+)

Compute from /time-series, or use /fx OHLC endpoints

List currencies

GET /list

GET /currencies

Authentication

?access_key=YOUR_KEY

X-API-Key header (keeps keys out of logs)

Response shapes

Before and after.

The pair-key concatenation goes away: quotes["USD" + code] becomes results[code]. "source" is "base", unix "timestamp" is ISO-8601 "updated", and the "success" flag is replaced by HTTP status codes.

Before · CurrencyLayer
$ curl "https://api.currencylayer.com/
   live?access_key=KEY&currencies=EUR,GBP"

{
  "success": true,
  "timestamp": 1757490000,
  "source": "USD",
  "quotes": {
    "USDEUR": 0.859587,
    "USDGBP": 0.738035
  }
}
After · fastFOREX API
$ curl -H "X-API-Key: YOUR_KEY" \
   "https://api.fastforex.io/fetch-multi?from=USD&to=EUR,GBP"

{
  "base": "USD",
  "results": {
    "EUR": 0.859587,
    "GBP": 0.738035
  },
  "updated": "2026-09-10T09:39:00Z"
}

Watch for these differences.

The honest list — everything that behaves differently, including the ones that work in your favour.

  1. Concatenated pair keys

    CurrencyLayer keys quotes as "USDEUR". If your code slices the first three characters off every key, that workaround can be deleted — our results are keyed by plain currency code.

  2. Source-currency switching is free here

    Changing the source/base currency is a paid CurrencyLayer feature. Every fastFOREX API plan supports any base currency.

  3. Free-plan cadence differs

    CurrencyLayer's free plan updates daily (not hourly like its siblings). If you calibrated caching around that, our 60-second updates change your freshness assumptions — pleasantly.

  4. XAU/XAG as currencies

    CurrencyLayer exposes gold and silver as currency codes. On fastFOREX API, metals live in the dedicated Metals API with units, purities and bid/ask — map those calls to /metals/spot.

Prove it to yourself

Benchmark both during your trial.

Don't take our 21ms average on faith. Run both APIs from your own infrastructure with this snippet, compare the numbers, and cut over when the data says so.

benchmark.sh · run from your servers
$ for i in 1 2 3 4 5; do
>   curl -s -o /dev/null -w "fastforex     %{time_total}s\n" \
>     -H "X-API-Key: KEY" "https://api.fastforex.io/fetch-all?from=USD"
>   curl -s -o /dev/null -w "currencylayer %{time_total}s\n" \
>     "https://api.currencylayer.com/live?access_key=KEY"
> done

fastforex     0.021s
currencylayer 0.052s

Switching support included.

Our team answers 365 days a year and has guided many migrations from this exact provider. Need longer than 7 days to validate? Ask about extending your trial.

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Migration questions.

What teams ask when leaving CurrencyLayer.

Can I run both APIs in parallel?
Yes — the recommended path. Shadow-read against both providers during the 7-day trial and compare values and latency on production traffic before switching.
Is migrating from Fixer or ExchangeRatesAPI.io the same process?
Nearly — all three are APILayer products with similar APIs, though CurrencyLayer's concatenated pair keys are unique to it. We publish separate guides for each.
Will historical values match?
Close but not identical — different sources and snapshot times. Keep your CurrencyLayer-era records as-is and source new history from us, or backfill from our 55+ years for consistency.
Can you help with the migration?
Yes — support answers 365 days a year. If you need more than 7 days to validate, ask about extending your trial.

Something specific to your setup?

Send us your current integration details and we'll map it for you.

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An hour of work for 60x fresher data.

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