Prince William wore an Irish Guards mounted officer's uniform in Guard of Honour Order with a forage cap, rather than the bearskin hat.
As a serving Royal Air Force flight lieutenant who also held the equivalent Royal Navy rank of lieutenant and army rank of captain in the Blues and Royals, William could have chosen to wear the uniform of any of these junior officer ranks.
 However, as he had been appointed colonel of the Irish Guards on 10 February 2011, he opted instead to wear the full dress uniform of that regiment.
As a Knight of the Order of the Garter, he wore the order's star and blue riband, to which were affixed his RAF wings and Golden Jubilee Medal.
William did not wear a sword in the church.

Prince Harry wore the uniform of a captain of the Blues and Royals (Royal Horse Guards and 1st Dragoons), with a forage cap.
He wore aiguillettes, a cross-belt and gold waist belt with sword slings, but no sword.
He wore the wings of the Army Air Corps and Golden Jubilee and Afghanistan Campaign medals.

Designer Russell Kashket worked with the Princes to address concerns they had with the outfits.
One such concern was the heat of the Abbey, so the designers used special material to absorb the heat while still achieving the desired look.
Further, military dress uniforms do not traditionally have pockets, but the palace requested that some sort of compartment be added to Harry's outfit so that Catherine's wedding ring would not be lost.
Prince William wore an Irish Guards mounted officer's uniform in Guard of Honour Order with a forage cap, rather than the bearskin hat. As a serving Royal Air Force flight lieutenant who also held the equivalent Royal Navy rank of lieutenant and army rank of captain in the Blues and Royals, William could have chosen to wear the uniform of any of these junior officer ranks.  However, as he had been appointed colonel of the Irish Guards on 10 February 2011, he opted instead to wear the full dress uniform of that regiment. As a Knight of the Order of the Garter, he wore the order's star and blue riband, to which were affixed his RAF wings and Golden Jubilee Medal. William did not wear a sword in the church.
Prince Harry wore the uniform of a captain of the Blues and Royals (Royal Horse Guards and 1st Dragoons), with a forage cap. He wore aiguillettes, a cross-belt and gold waist belt with sword slings, but no sword. He wore the wings of the Army Air Corps and Golden Jubilee and Afghanistan Campaign medals.
Designer Russell Kashket worked with the Princes to address concerns they had with the outfits. One such concern was the heat of the Abbey, so the designers used special material to absorb the heat while still achieving the desired look. Further, military dress uniforms do not traditionally have pockets, but the palace requested that some sort of compartment be added to Harry's outfit so that Catherine's wedding ring would not be lost.
Wedding of Prince William and Catherine Middleton