Whisk the flour and salt in a large bowl until evenly combined. (Or see notes for blender method.)
Add the eggs and about half the milk. Whisk until thick and smooth, with no dry pockets.
Whisk in the remaining milk, then the melted butter. The batter should be smooth and fluid, about the consistency of heavy cream.
Let the batter rest at room temperature for a few minutes while you preheat a large nonstick skillet or crepe pan over medium heat.
Lightly butter the surface. Pour a generous 1/4 cup batter into the pan. Immediately swirl to coat the bottom in a thin, even layer (you may want to use a little more for a large pan).
Cook until the edges look dry and the underside is lightly golden, about 45 to 60 seconds. Flip and cook another 20 to 30 seconds.
Transfer to a plate and repeat with remaining batter, lightly buttering the pan as needed. Stack crepes as they cook and cover with a clean towel to keep them soft.
Notes
Blender option: I often make them in the blender. I place the blender canister on my kitchen scale, tap the "Metric" button in the recipe card, then add everything by weight. Only one dish to clean and no measuring cups needed. Then once I'm done making crepes, I run the blender with hot water and dish soap to clean it. Batter consistency: The batter should be thin enough to spread easily when swirled. If crepes tear, the batter is too thin. If they turn out thick and cakey, thin with a little more milk.Keep them soft: Cover finished crepes with a clean towel or inverted bowl as they cook so the trapped steam keeps them flexible.Make ahead: Crepes can be made ahead and refrigerated for up to 3 days, with parchment between each one. Freeze for up to 2 months in a zip-top bag.Reheat: Warm in a skillet over low heat for 30 seconds per side, or in a 300°F oven between damp paper towels for 5 to 10 minutes.First crepe is a test: it often fails. Use it to check pan temperature and batter thickness before committing to the rest of the stack.