a voluntad

at will

→ a
phrase Rare #48,703
at will Used when something is done freely, whenever one wants, or under one’s own control.
SP: Puedes cambiarlo a voluntad.
EN: You can change it at will.

Él podía hacer de todo a voluntad.

He could do anything he wanted.

Puedes ir y venir a voluntad.

You can come and go as you please.