GreenAddress is the first bitcoin wallet to launch a replace-by-fee option in transactions with which users can increase fee on their transactions.

Replace-by-fee is a mempool policy. Mempools are collections of unconfirmed transactions stored by full nodes. They are used by miners to select transactions to include in blocks. As a result of this, users by just clicking a button can increase fee on their transactions.

This Replace-by-fee allows mempool transactions to be replaced by newer transactions provided they have a higher fee. In case of heavy transaction load, the feature can help transaction get ‘unstuck.’ There has been disputes and fear among critics that this feature might harm reliability of unconfirmed transactions.

Replace-by-fee might disadvantage Bitcoin payment processors that effectively built their business on instant payments. Also it might negatively affect merchants selling digital goods and physical goods. And customers would be disadvantaged if this service stops accepting bitcoin transactions.

The company blog stated that, GreenAddress have been advocating for replace-by-fee since as early as April 2014 and this is the first time it has been implemented. The main reason behind this is that transactions are constantly getting stuck and unconfirmed transactions for hours or even days will occur, which is incredibly frustrating for bitcoin users.