Convert currencies using data from configurable currency rates providers.
With Currency Converter you can select different Exchange Rates Providers to get faster updates, more options, and a wider set of currencies. Most commercial providers also offers a free version, but with some caveats, as for example not being able to request a base currency, with the result that each time you request one new currency pair, all of them will be downloaded. So unless you really need to, I strongly recommend sticking with the default.
For the average traveller or businessperson the default selection should be more than enough.
Currency Converter keeps an internal list of registered, legal currencies, which is used together with a list of the currencies offered by the chosen provider. The latter is refreshed when the app is loaded, except if there is no network connection, or if you have explicitly chosen to work offline. For this Currency Converter uses an effective caching mechanism. Based on the update interval of the current provider, and timestamps on each currency pair (e.g. EUR/USD) it only fetches online rates when needed - or, again, when explicitly told to.
You can choose to force refresh for one pair or all the rates for the currently selected "From" currency.
The list of available currencies is generated from the 'From Currency' you had selected when the app is loaded or when you chose to refresh the cache. This means, that if you change the 'From Currency' right after you go offline, there is no guarantee that a list of the available currencies can be generated from the cache. To remedy this, change to the 'From Currency' you need to be cached, and select "Refresh cache for ". In theory you can cache the currencies you need, and use the app offline for as long as you trust the cached exchange rate.