Warn Review 2026: Free Shopify Prop 65 & Warning Popups

This is the most quietly useful app in this batch, and almost nobody goes looking for it until they need it badly. Selling regulated, restricted or hazardous products means you routinely need to tell a specific customer a specific thing before they buy: this cannot ship to your state, this contains a chemical California requires us to warn you about, this is made to order and cannot be returned, this requires a signature on delivery. Most stores handle that by burying a line in the product description and hoping. That is not a control, it is a wish.

The feature that makes this a real compliance tool rather than a decorative notice is the ability to block the checkout process while the warning is displayed. There is a genuine difference between information a customer may have scrolled past and a gate they had to pass through, and if your reason for showing the warning is legal or safety-related, that difference is the entire point. Combined with country-level geolocation targeting, you can enforce a rule that applies in one market without adding friction anywhere else, which is exactly the shape of most real-world shipping and regulatory restrictions.

Two things temper the enthusiasm. It has only 16 reviews, which is a very thin base even at 4.9, so it is far less proven than the developer’s larger titles. And no app can tell you what your legal obligations are; it gives you a mechanism to meet obligations you have already established with someone qualified. But it is free, with no paid tier and no development-store restriction, which makes the decision easy for any store that has ever needed to warn a customer about something. Compared with paying a developer to build conditional checkout logic, this is an obvious first thing to try.