What type of grout do I use with a glass tile backsplash?

Sanded grout is for big grout lines and non-sanded is for very small grout lines. I would ask where you got the tile, but likely non-sanded.

Lora is correct! Sanded grout for wide gaps, mainly used on floors. Unsanded for narrow gaps. You case use unsanded grout.

Unsanded for sure... If your tile is transparent, make sure to use the right mortar (thin-set) and it is applied properly so you don't see trowel lines through the tile.

Good luck! Would love to hear how it goes because I'm gearing up for a similar project 😀

Be sure to prepare the walls properly with a good thorough cleaning, use PST (degreasing cleaner) and rise well. Follow instructions on the thin-set (adhesive) and use the right tools. Make sure they are close to hand when you are ready to start. (Local rental center should have cutters, trowels etc... so you wouldn't need to buy them for small projects). Have fun!!!

Sanded grout is for not only wide (1/2 inch and wider) grout lines, but also for outdoor applications.