According to Michelin star chef José Andrés, cracking an egg open by hitting it against the rim of something, like a bowl or measuring cup, is downright dreadful and detrimental.
When an egg hits a convex edge, the force can mix up the yolk and egg white, cause broken shell bits to get mixed with what’s inside, and spoil everything if the shell is tainted.
Andrés suggests tapping eggs on a flat surface like a counter or cutting board. Once you get a crack in the middle, use your thumbs to dig further into the egg and split the shell.
If you aren't confident in your egg-cracking abilities, practice cracking an egg open into a spare bowl before you try to crack one directly into a hot pan or bowl of brownie mix.