Plain corn chips, plain potato chips, popcorn, nuts and most rice cakes are gluten free. The failures cluster in seasoning blends, in malt vinegar flavouring, in shared fryers, and in anything described as "multigrain."
A category where the base food is nearly always safe and the flavouring nearly always decides the answer.

Seasoning blends are the main route. Hydrolyzed wheat protein is a cheap savoury base, malt vinegar powder is standard in salt-and-vinegar flavouring, and soy sauce powder turns up in barbecue and teriyaki styles. A plain chip and a flavoured chip from the same bag family can give different answers.
"Multigrain" chips are the category's worst piece of naming. They usually contain wheat, and they are marketed alongside corn chips in a way that invites the wrong assumption.
Pretzels are wheat by definition. A pretzel is a wheat dough boiled in alkaline solution. Gluten-free pretzels exist as a separate product.
Shared fryers matter here too: some kettle chips and most restaurant tortilla chips are fried in oil that also handles breaded food.
Point CiCi at the barcode and get this same reasoning in about two seconds, plus the carbs and whether it has been recalled. 360,000+ packaged foods are already read and waiting.
Sorted by what the answer actually is, rather than alphabetically — because the useful question in a shop is “which pile is this in.”
Usually contain wheat despite sitting next to the corn chips.
Wheat dough by definition. Gluten-free versions are a separate product.
Wheat unless specifically made from rice, seeds or nuts.
Malt vinegar powder is standard in this flavour.
Hydrolyzed wheat protein and soy sauce powder both appear.
Plain nuts are fine; seasoned and honey-roasted versions often use wheat starch or soy sauce.
Pretzel and cookie pieces are common inclusions.
Potato, oil, salt.
Corn, oil, salt. Restaurant chips may share a fryer.
Corn. Flavoured varieties follow the seasoning rule.
Puffed rice. Check flavoured versions for soy sauce and malt.
Plain salted chips almost always are. Flavoured ones depend on the seasoning. Salt and vinegar frequently uses malt vinegar powder from barley, and savoury flavours often use hydrolyzed wheat protein.
Plain popcorn is corn and is gluten free. Flavoured microwave and ready-to-eat popcorn follows the seasoning rule, and some caramel and "movie theatre butter" styles contain wheat-derived ingredients.
Usually not. Multigrain means several grains and wheat is typically among them. The name sits uncomfortably close to corn chips on the shelf, which is why this one catches people.
This site answers the question you knew to ask. The app answers the one you didn't: the barley malt in a rice cereal, the wheat starch in a gummy. Scan the barcode, or photograph the panel when the barcode isn't in any database, and CiCi shows which words on the label produced the answer.
14 days free, then $29.99 a year. Cheaper than Fig, and it does what three separate apps do. This website stays free forever either way: every answer on it, permanently, with no account.