The 27-year-old winger, who joined the Terriers from Wolves in January 2013, was under contract until next summer but leaves the John Smith’s Stadium with immediate effect on Tuesday.
Town boss Chris Powell told the Championship club’s official website: “After discussions with Adam, we made the decision that this was the best option for everyone concerned.
“The timing gives Adam the chance to find himself another club and make a clean start in his career.
“Adam has worked diligently during my time as manager and I believe I speak for everyone at Huddersfield Town when I wish him the best of luck for the future.
“He will always be a friend to everyone here.”
The Liverpudlian made 64 league appearances for Huddersfield in total, scoring six goals, but spent most of the 2014-15 season on loan at Rotherham.