Long since launched in 2009 Bitcoin is no longer the only virtual currency, which should represent an alternative to conventional money. For some time, other cryptocurrencies have been conquering the market, no longer based on banknotes or coins, but on cryptographic keys. They are known by the name Altcoins. What they all have in common is that, like Bitcoin, they are not controlled by state authorities, but by the users themselves. The basis is a peer-to-peer network that works completely without authorities and supervisors like banks. This is privately generated money. Especially in memory of the recent financial crisis and in the eyes of many obvious failures of banks and governments this principle seems to some contemporaries as tempting. On the other hand, there are great doubts as to whether such alternative currencies will be sustainable. The different altcoins are distinguished by different properties of each other and bitcoins. The strengths and weaknesses of the most important representatives can be seen in our Altcoin comparison.