When you go to the grocery store to pick out a carton of eggs, you’ll be confronted with seemingly endless choices about the size, color, and quality of your eggs. Do you get brown eggs or white, jumbo or extra-large? There’s also the matter of grading—because what exactly is the difference between Grade AA and Grade A eggs besides the letters featured on the seal? Grade B eggs are usually less expensive than the other two grades, but are those even worth your time and hard-earned money? There are also ungraded eggs, but venturing into that world somehow seems dangerous when there are certified eggs readily available.
The letter grade depends solely on quality, rather than volume or weight, and a higher grade from the United States Department of Agriculture, which does these inspections, means a higher quality egg. But “quality,” in this case, only refers to exterior and interior quality, rather than nutritional value, size, or safety, so there’s no real reason to freak out about ungraded eggs, or getting an egg with a lower quality. All eggs must be inspected for "wholesomeness," whatever that means (though I assume it has something to do with safety), and grading isn’t actually mandated by the USDA.
The highest egg grade is AA, followed by A, then B, and the letter takes appearance and both exterior and interior quality into account. According to the USDA guidelines, a Grade AA egg has “whites that are thick and firm; yolks that are high, round, and practically free from defects; and clean, unbroken shells.” Grade A eggs are basically the same except with whites that are only “reasonably” firm. Meanwhile, Grade B eggs can have some staining, and, according to the American Egg Board, “may be decidedly misshapen or faulty in texture with ridges, thin spots or rough areas.”
So all eggs in the supermarket, regardless of grade, are safe to eat, and really, the main differences between the egg grades are superficial. If you’re going to be frying or poaching an egg, getting a higher grade will make for a prettier plate. But if you’re just cracking a couple to make an omelette or put in a cake, go for a lower grade—or don’t. They’re just eggs at the end of the day.