What is french for know what I mean?

There are a few ways to say "know what I mean" in French, depending on the context and nuance you want to convey:

Formal:

* Vous voyez ce que je veux dire ? (You see what I mean?)

* Comprenez-vous ce que je veux dire ? (Do you understand what I mean?)

Informal:

* Tu vois ce que je veux dire ? (You see what I mean?)

* Tu comprends ce que je veux dire ? (Do you understand what I mean?)

* Tu sais ce que je veux dire ? (You know what I mean?)

* C'est ça, non ? (That's it, right?)

Slang:

* Tu piges ? (You get it?)

* Tu captes ? (You get it?)

The best choice will depend on the specific situation and your relationship with the person you are speaking to.