Genshin Impact Character EXP farming isn't particularly effective, as killing enemies doesn't provide much experience, but it is possible. Here are the fastest ways to level up your characters.
Genshin Impact Character EXP Farm: Fastest Ways to Level Up
The best way to level up characters is using EXP material found around the world. Wanderer's Advice is worth 1,000 EXP, Adventurer's Experience is worth 5,000 EXP, and Hero's Wit is worth 20,000 EXP. These items can be found in treasure chests and as rewards for finishing Domains and quests.
Adventurer's Experience can be farmed by activating the Blossom of Revelation Ley Line Outcrops that can be found around the land, and are visible on your map. Activating these will spawn enemies to defeat — not so great on its own — that will allow you to claim a reward of around 13 Adventurer's Experience in exchange for 20 Resin.
Provided you have the mora to afford it, this will likely be the most effective way for you to level up your characters as quickly as possible.