21-year old winger Scannell has agreed a new four-and-a-half-year deal with the Eagles whilst 18-year old midfielder Williams has signed on for three-and-a-half years and both are delighted to commit themselves to the Palace cause.
"I am really happy to have signed the contract with this club; it is the only place I want to be. I am so pleased that the boss has offered me a new deal," Scannell told the club's official website.
Whilst Williams added: "It is great for me to be signing, especially a deal of this length. It has been great to be involved in the first team so early in my career."