Available features:

Free tier: 

The free tier grants access to three endpoints that provide the following features:

- GetSymbols: returns all the available symbols on Fixer.

- GetLatestValues: returns the latest available FX rates for a given set of currencies.

- GetHistoricalValues: returns the latest FX rates for a given set of currencies on a given date.

In order to use this, create an account on Fixer.io and configure the API key.

Paid tier:

You can request a trial for this (thanks Andreas and Fixer support team):

- Convert: converts two currencies with the latest or historical values.

- GetTimeseries: lists all the values of a given set of currencies between two dates.

- GetFluctuation: lists the difference between two dates on a set of currencies.

The Convert has a workaround: there is a function that converts the values against available values. Additional improvements on this are on the way!