Is ketchup gluten-free?

Yes, in almost every case. Ketchup is built from tomato concentrate, vinegar, sugar or corn syrup, salt, onion powder, and spices — none of which are gluten-containing on their own.

Why the answer is usually a clean yes

Standard ketchup doesn't rely on wheat, barley, or rye for its texture or flavor the way many other condiments do. The vinegar used is almost always distilled, which is gluten-free regardless of the grain it started from, as covered on this site's vinegar page. Malt vinegar — the one type that isn't safe — is rare in ketchup specifically, more of a concern in specialty mustards and some barbecue sauces.

The two things actually worth checking

• Modified food starch as a thickener. Most modified food starch used in US food manufacturing is corn-based, but it can occasionally be wheat-based. It's a low-probability check, not a high-probability one, but it's the reason "check the label" still applies to an otherwise simple product.
• Shared-facility statements. Some ketchup is made in facilities that also process wheat-containing products, which can show up as a "may contain wheat" advisory. This doesn't mean the product itself contains gluten, but it's worth knowing if you're highly sensitive.

Practical guidance

Plain ketchup is safe to treat as a default yes without much second-guessing. If you want more certainty than that, look for a "gluten-free" label or certification specifically — many ketchup brands are naturally gluten-free without ever going through certification, so the absence of a label isn't itself a warning sign, just less information than a labeled product gives you.

FAQ

Does ketchup ever contain malt vinegar? It's uncommon, but check the label on specialty or gourmet ketchups the same way you would for mustard.

Is unlabeled ketchup safe if the ingredients look clean? Generally yes — many manufacturers don't bother certifying a product that's naturally gluten-free. A clean ingredient list is a good sign even without a label.

Sources

• Celiac.com, "Is Ketchup Gluten-Free and Safe for People with Celiac Disease?"
• Celiac.com, "Is Ketchup Gluten-Free? Safe Brands, Ingredients, and Label Tips"