Hardfolio uses these websites to get its data. All these websites use encryption so that when Hardfolio talks to their servers, external parties cannot read the data transfer. Crypto Compare is used to get information about various coins, images and most importantly price estimations in your local currency. Other websites are used to get address balances.
For privacy issues and other information about Hardfolio, please see this article. These servers are only used to retrieve information about your Crypto Currency holdings.
Trezor (Hardware Wallet)
CryptoID (Bitcoin, Litecoin, Dash, Digitbyte, Vertcoin)
BlockCypher (Ethereum, Dash, Dogecoin, Bitcoin)
Block Explorer (Bitcoin, ZCash)
So Chain (Doge, Bitcoin, Dash, Litecoin)
BlockDozer (Bitcoin Cash)
Bitcoin Gold Blocks (Bitcoin Gold)
Gastracker (Ethereum Classic)