Rice, sorghum, almond, coconut, cassava, buckwheat, teff and oat flours are gluten free. The two things that catch people are wheat starch, which appears in some European gluten-free blends and is legal there, and shared milling, which affects naturally gluten-free grains more than people expect.
Flour is the category where a naturally gluten-free ingredient most often arrives contaminated, because milling equipment is expensive and rarely dedicated.

Wheat starch is the category's most counterintuitive entry. It is wheat, but the gluten protein is washed out during processing, and specially processed wheat starch that tests below 20 ppm is legal in gluten-free products in the EU and UK, where it is common in prescription and commercial gluten-free bread. In the US it is permitted only if the finished food still meets the 20 ppm limit. Practical rule: wheat starch inside a product carrying a gluten-free claim is compliant; wheat starch on a label with no such claim is a stop sign.
Teff is worth a note because several ingredient databases have it wrong. Teff is an entirely gluten-free grain. It appears in some gluten warning lists through taxonomy errors, and CiCi corrects for that.
The binder question is separate from safety. Xanthan gum, psyllium and guar are what replace gluten's structure, and all three are gluten free.
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.”
All wheat or wheat hybrids.
Only when the oats are certified. See the oats guide.
Gluten washed out; legal in EU gluten-free products. Safe only inside a product carrying a gluten-free claim.
The workhorse base of most blends.
Ground nuts. Watch shared equipment in bulk bins.
Very absorbent. Not a 1:1 substitute.
From the same root; tapioca is the extracted starch.
Mild flavour, common in bread blends.
Unrelated to wheat despite the name. Shared milling is the only concern.
Gluten free. Several databases wrongly flag it — CiCi corrects this.
Structure replacements for gluten. All gluten free.
Specially processed wheat starch has the gluten protein washed out and can test below 20 ppm. It is legal in gluten-free foods in the EU and UK and common in gluten-free bread there. The safe reading is: wheat starch inside a product that carries a gluten-free claim is compliant; wheat starch on a label with no claim should be treated as wheat.
Yes, entirely. Buckwheat is not related to wheat. It is a seed from a plant in the rhubarb family. The only real question is whether it was milled on shared equipment, which a gluten-free claim resolves.
Only with a blend formulated as a 1:1 replacement, which includes a binder such as xanthan gum. Single flours behave very differently: coconut flour absorbs several times more liquid, and almond flour provides no structure at all.
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.