What does friendship level do?

I've seen in the menus that each character, except the traveler, has a 'friendship' level. It seems to be linked to how long the character has been in the active party and, if I read right, caps at 10.

But what does it actually do?

Solution 1:

Raising a character's friendship level:

• Unlocks more of their lore/background story and voice lines (accessible via the Profile section on the Character screen);
• Unlocks more interactions with the character when they are set as a companion in your Serenitea Pot;
• Unlocks more facial expressions that you can choose when taking a photo;
• Gives you the character's namecard that you can set on your profile once you reach friendship level 10.

Additionally, you will earn achievements (and therefore Primogems) for reaching friendship level 10 with 4/8/16 different characters. Check out the Genshin Impact wiki for complete information on friendship levels.

As far as I know friendship level has no effect on the character's combat ability/stats.

Solution 2:

Freindship levels gives you the lore and the story of this world presented in an interesting way like voice lines and how they feel about stuff. The friendship mechanic mostly focuses characters lore. Each character has a story, origin, and special life lessons. So, every one of them gets a differnt friendship level. As of rght now it does not effect combat at all.