What does black tie optional mean?

The short answer

Black tie optional means a tuxedo is welcome but a dark suit and tie is equally correct, and for women a floor-length gown, a formal midi or dressy separates all work. It is the couple saying they want a formal evening without requiring anyone to rent a tuxedo.

At a glance

White tie: Tailcoat; floor-length ball gown.
Black tie: Tuxedo required; floor-length or very formal midi.
Black tie optional: Tuxedo or dark suit; gown, formal midi or dressy separates.
Cocktail: Suit and tie; knee-length or midi dress.
Dressy casual: Sport coat, no tie needed; nice dress or smart separates.
Casual: Smart, never jeans unless the couple said jeans.

The codes, from most to least formal

White tie. Rare. Tailcoat, white waistcoat and bow tie; floor-length ball gown. If you are invited to one, the invitation will make it unmistakable.

Black tie. Tuxedo required; floor-length gown or a very formal midi. Not a suggestion.

Black tie optional or formal. Tuxedo welcome, dark suit and tie equally fine. Gown, formal midi, or dressy separates.

Cocktail. The most common code in the US. Suit and tie; knee-length or midi dress. Not floor-length, not a sundress.

Dressy casual or semi-formal. Sport coat, no tie required; a nice dress or smart separates.

Casual. Still means smart. Chinos and a collared shirt, a sundress. Never jeans unless the couple has said jeans.

The invented ones

Garden party, beach formal, festive, dusty-blue-and-sage - couples increasingly write their own. These are aesthetic requests rather than formality levels, and the reliable move is to read the formality from the venue and time, then apply their colour or mood note on top.

'Festive' almost always means cocktail attire with something celebratory about it. 'Beach formal' means formal fabrics and flat shoes. 'Garden party' means cocktail with a print and a shoe that survives grass.

When in doubt

Check the couple's wedding website, which usually elaborates. If it does not, dress to the more formal reading — being slightly overdressed at a wedding is invisible, and being underdressed is not.

Common questions

What does black tie optional mean for a guest?

A tuxedo is welcome but a dark suit and tie is equally correct. For women, a floor-length gown, a formal midi or dressy separates all work. The couple wants a formal evening without requiring anyone to rent a tuxedo.

What does cocktail attire mean for a wedding?

A suit and tie, or a knee-length or midi dress. It is the most common dress code at American weddings - dressier than a sundress, less formal than a floor-length gown.

What does festive attire mean at a wedding?

Almost always cocktail attire with something celebratory about it - colour, sparkle or pattern. It is an aesthetic request rather than a formality level.