Unfortunately, there's currently no way to increase a character's inventory size in the game, meaning players are stuck with what they have in that regard. Between these two features, players are forced to think wisely about which materials they pick up and take with them on their journeys, as it's rather annoying finding one's carry weight maxed out and being unable to pick up a rare material. Like most survival games, Valheim restricts how much players can carry on them with inventory size and carry weight limits.
