Lloyd Williams has played 45 games for the Blues since making his debut against Leinster in Cardiff in March 2010. The former Cowbridge Comprehensive student made his international debut against Argentina during the 2011 Rugby World Cup.
Cardiff Blues Director of Rugby Phil Davies said of the signings,
"Without a doubt Lloyd is a key player for us.
"When you look at my 25 rule, where we want to have 25 players under 25 in the squad, he, Lewis Jones, Tom Williams and Tom Davies all fit the bill.
"Lloyd is vitally important to the squad, we build a team around people like Lloyd.
"Lloyd is establishing himself in the Wales squad now and our aim for him is to go with Wales to the next World Cup as number one Scrum Half.
"That is a challenge for him personally and there is a challenge for him here at the Blues with Lewis Jones developing well. We are very pleased to have two outstanding Scrum Halves here."
"Tom Williams is a young player who was going to be in our Academy player this year but we gave him his opportunity in pre-season and he came through. He has played a bit of rugby for Cardiff this year and has impressed us."
"He made his league debut against the Dragons at Full Back and went on the Sevens tour but unfortunately dislocated his shoulder against Saracens a few weeks ago, but should be back in May.
"He is one that we have nurtured through the system, we are developing good depth and versatility with our Full Backs.
"He is another player who at 20 years of age, we have for another three years. He is a real quality individual who is getting better and better.