How do you say in a blink of an eye french?

There are a few ways to say "in a blink of an eye" in French, each with a slightly different nuance:

Formal:

* En un clin d'œil: This is the most literal translation and is quite common. It's a bit more formal and often used in writing.

Informal:

* En un éclair: This means "in a flash" and has a similar meaning to "in a blink of an eye." It's more casual and commonly used in spoken French.

* En un instant: This means "in an instant" and is another good option for informal speech.

* En un tournemain: This means "in a jiffy" or "in a flash." It's a bit more colloquial and less formal than the other options.

Examples:

* La voiture a disparu en un clin d'œil. (The car disappeared in a blink of an eye.)

* Il a fini son travail en un éclair. (He finished his work in a flash.)

* Elle est partie en un instant. (She left in an instant.)

* Il a réparé la machine en un tournemain. (He fixed the machine in a jiffy.)

The best choice for you will depend on the context and the level of formality you want to achieve.