What can you actually bring through TSA?

The core carry-on rule is 3-1-1: liquids, gels, aerosols, creams, and pastes in containers of 3.4 ounces (100 ml) or less, all fitting in a single quart-sized clear bag, one bag per passenger. Size of the container is what counts, not how full it is, so a half-empty eight-ounce bottle gets taken. Medically necessary liquids, breast milk, and formula are exempt in reasonable quantities but should be declared at the checkpoint. Solid food is generally fine in carry-on, while spreadable and pourable foods, peanut butter, yogurt, hummus, soups, jams, count as liquids and lose to the 3-1-1 rule.

Beyond liquids, the sorting is mostly about whether something could be used as a weapon: no knives, box cutters, or most tools over seven inches in carry-on, though they can go in checked bags. Lithium batteries and power banks are the reverse, they must fly in the cabin, never in checked luggage, because of fire risk. Firearms are checked only, unloaded, in a locked hard case, and declared, and being casual about that carries serious penalties. When in doubt, TSA's own What Can I Bring tool answers by item, and their social accounts field questions directly. Final officer discretion is real, so anything valuable, irreplaceable, or oddly shaped is safer packed in a way that survives a no.