By which they mean "the real-time mid-market rate is something that some unnamed provider made up and claims is representative of actual rates."
They give EUR/USD to two digits of precision. The actual spreads quoted by anyone who isn't trying to utterly screw you over is much, much tighter than 0.01. Different parties will have different ideas of the current and historical bids and offers.
Using a service like this is probably fine for display purposes and maybe okay for some accounting purposes as long as no one is going to audit it or care about the results being entirely correct. Using it for transactions would be a bad idea.
When Forex prices flash across cspan or similar they are typically quoting the interbank offered rate. Retail traders don’t get anything close to this rate. You usually go through several intermediaries who each add a spread. There’s not best price law in fx.
Using prices from retail fx brokers usually isn’t a good idea either since their spreads are so outrageous. Oanda has reasonable rate info I’m told, but it’s more geared for professional traders.
What's wrong with averaging them together? That should negate the spread unless they're really short of one currency and long on the other. I guess your local bank would post bad rates on some pairs because of their carrying costs, but someone like transferwise?
Back in 2009, I recall one Canadian bank having competitive rates when you wanted to sell them USD, but terrible rates when you wanted to buy their USD. I guess they were in dire need for USD and didn't want to sell what they had to their retail customers.
If you’re just doing it for a retail perspective some sort of averaging scheme like you mentioned would probably be okay. If you’re dealing with large amounts regularly you’d probably want to negotiate with multiple liquidity providers to get an idea of what kind of rates you’d get for a given currency pair.
It's funny how much was based on LIBOR when it provided zero indication of depth-of-market for the banks feeding it numbers.
USD, JPY, BGN, CZK, DKK, GBP, HUF, PLN, RON, SEK, CHF, ISK, NOK, HRK, RUB, TRY, AUD, BRL, CAD, CNY, HKD, IDR, ILS, INR, KRW, MXN, MYR, NZD, PHP, SGD, THB, ZAR
Here's a better alternative, updated every minute: http://cryptomarketplot.com/api.json
It has the bid and ask (apparently missing given the comments below). For fiat/fiat pairs, use the BTC/fiat pair, for example:
"name": "Turkish Lira",
No rate limit, no condition to use the api. It's free for all and will remain free.
However, most people will not be able to trade at the XE quoted rates. Just try to go to your back and exchange. The price reported on CMP are what any random person can get, for real, using the crypto exchanges - without complicated paperwork. Without delay. With a separate bid and ask, instead of reporting a theoretical midpoint.
Also, the API is fully free. Anytime. Any volume of request. Commercial purposes included. No questions asked.
So yeah, that's currently smaller, but I think it is closer to what people and especially developers really care or need - the big fiat pairs, and true rates, without Terms-Of-Service.
 https://last10k.com/sec-filings/zen/0001463172-19-000445.htm... (scroll up a bit to see geographic information)