Audacious Swap — ruling 1

Casualty N means “As an additional cost to cast this spell, you may sacrifice a creature with power N or greater.” and “When you cast this spell, if a casualty cost was paid for it, copy it. If the spell has any targets, you may choose new targets for the copy.”

Audacious Swap — ruling 2

You may sacrifice only one creature to pay a spell's casualty cost, and you copy the spell only once.

Audacious Swap — ruling 3

If you pay the casualty cost of a spell, the copy will resolve before the original spell.

Audacious Swap — ruling 4

The copy of the spell is created on the stack, so it's not “cast.” Abilities that trigger when a player casts a spell won't trigger.

Audacious Swap : règles, fonctionnement et interactions (MTG)

Audacious Swap is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Casualty 2 (As you cast this spell, you may sacrifice a creature with power 2 or greater. When you do, copy this spell and you may choose a new target for the copy.) The owner of target nonenchantment permanent shuffles it into their library, then exiles the top card of their library. If it's a land card, they put it onto the battlefield. Otherwise, they may cast it without paying its mana cost.

How it works : Audacious Swap

Original English text — Wizards of the Coast / Scryfall

#1April 29, 2022· Wizards of the Coast
Casualty N means “As an additional cost to cast this spell, you may sacrifice a creature with power N or greater.” and “When you cast this spell, if a casualty cost was paid for it, copy it. If the spell has any targets, you may choose new targets for the copy.”
No other card is named in this ruling.
#2April 29, 2022· Wizards of the Coast
You may sacrifice only one creature to pay a spell's casualty cost, and you copy the spell only once.
No other card is named in this ruling.
#3April 29, 2022· Wizards of the Coast
If you pay the casualty cost of a spell, the copy will resolve before the original spell.
No other card is named in this ruling.
#4April 29, 2022· Wizards of the Coast
The copy of the spell is created on the stack, so it's not “cast.” Abilities that trigger when a player casts a spell won't trigger.
No other card is named in this ruling.