Carry-On vs. Checked Bag: What's the Difference?
The rules aren't really about which bag you use — they're about what's inside it, and a few categories flip completely between the two.
TSA doesn't restrict the bag itself — a suitcase or backpack is screened the same way whether it's checked or carried on, and size limits for the bag come from your airline, not security rules. What actually changes between carry-on and checked is what's allowed inside: some items are barred from one and required in the other, some just have a size limit that disappears once checked, and some don't change at all.
Must be carry-on, never checked
A small group of items are banned from checked baggage specifically because of fire risk — the cabin is the only place a crew member can respond if something overheats. This is the opposite direction from what people expect, since most restricted items get pushed toward checked bags, not away from them.
Must be checked, never carry-on
Bladed items are the clearest example of the reverse pattern. A pocket knife is banned from carry-on at any blade length, with no small-blade exception the way scissors get — but it's unrestricted once it's in a checked bag.
Where the size limit disappears
The 3.4 oz liquids limit is a carry-on-only rule. The exact same product — toothpaste, sunscreen, peanut butter — has no size restriction whatsoever once it's packed in a checked bag. If something is a liquid, gel, or spreadable food and you don't want to deal with the container-size math, checked baggage removes the limit entirely.
What doesn't change: the bag itself
TSA sets no size or weight rule for either a carry-on or checked bag — those limits are entirely up to your airline, and they vary by carrier and sometimes by fare class. A hard-shell, soft-shell, or backpack-style bag goes through the same screening either way.
Related rules
FAQ
- Why can't power banks go in checked bags if laptops can?
- A laptop's battery is installed inside the device, which TSA and airlines allow in checked bags (though carry-on is still recommended). A power bank or spare battery is a loose, uninstalled battery with no device around it — those are barred from checked baggage entirely because of fire risk.
- Does TSA set carry-on bag size limits?
- No. Bag dimensions and weight limits are set by your airline, not TSA. TSA only screens the contents of the bag.