Prop 65 warnings for online sellers: when you need one and where it goes on a listing

An online seller needs a California Proposition 65 warning on a listing when the product itself needs one: when it exposes buyers to a chemical on California's list above the level the rules set, and the package or the supplier's documents carry a Prop 65 warning. Since 1 January 2025, an online Prop 65 warning goes on the product display page, behind a clearly marked hyperlink using the word WARNING, CA WARNING or CALIFORNIA WARNING, or in another prominent warning shown before purchase, and a new short-form warning must name at least one chemical. The older short form without a named chemical stays acceptable until 1 January 2028, and during that transition internet retailers have 60 days to update a website warning after notice from the manufacturer or distributor.

What is Prop 65?

Proposition 65 is a California law that asks businesses to warn consumers before exposing them to chemicals on the state's list of chemicals known to cause cancer, birth defects or other reproductive harm. California's Office of Environmental Health Hazard Assessment (OEHHA) sets the warning rules and publishes guidance for internet and catalogue sales.

Prop 65 does not ban products. Prop 65 asks for a warning when a listed chemical is present above the level the rules set, unless an exemption applies. A Prop 65 warning is not an admission that a product is unsafe: it is the notice the law asks for, and it appears on many everyday products. Whether a product needs a Prop 65 warning depends on what the product contains and how much, so the answer usually comes from the maker or a laboratory test, not from the listing.

Who is responsible for a Prop 65 warning?

The Prop 65 duty sits mainly with the businesses that make, import and distribute a product, and online retailers are in the chain too. During the transition to the new short form, internet retailers have 60 days to update their website warnings after they receive notice from the manufacturer or distributor that a new warning is required.

Where does a Prop 65 warning go on an online listing?

A Prop 65 warning for a product sold online must reach the buyer before purchase. Under the amendments in effect since 1 January 2025, the online warning can be given in one of three ways:

1. On the product display page.
2. Through a clearly marked hyperlink on the page, using the word WARNING, CA WARNING or CALIFORNIA WARNING.
3. In another prominently displayed warning shown before the purchase is completed.

The 2025 amendments also removed an earlier requirement for products sold online to carry the warning both on the website and on the product itself. A product whose package carries a Prop 65 warning should keep it, and the listing should show the same warning.

What changed in the Prop 65 short-form warning?

The Prop 65 short-form warning is the brief version many products use on small labels. From 1 January 2025, a short-form warning "must specify at least one chemical for which the warning is being provided", and both short and long warnings may use CA WARNING or CALIFORNIA WARNING as the signal word in place of WARNING.

A transition runs from 1 January 2025 to 1 January 2028, during which the older short-form warning without a named chemical is still treated as clear and reasonable. Products made and labelled during the transition with the old short form can continue to sell, new labels should move to the new form, and each listing should match the label on the product it sells.

What does a Prop 65 warning contain?

A Prop 65 warning has fixed parts, and OEHHA's guidance shows the approved forms. A Prop 65 warning generally has:

• A signal word: WARNING, or since 2025 CA WARNING or CALIFORNIA WARNING.
• The harm: cancer, reproductive harm, or both.
• The chemical, named; since 2025 the short form must name at least one.
• Where to learn more, a pointer to the state's warnings website, in the forms that include it.

Because the parts of a Prop 65 warning are fixed, a warning that has been rewritten, shortened or loosely translated may no longer be a valid warning.

Should the listing copy the Prop 65 warning exactly?

Yes. A listing should use the exact Prop 65 warning on the product's label, word for word, with the same signal word and the same chemical named. Four mistakes to avoid:

• rewriting the Prop 65 warning in your words
• shortening a long Prop 65 warning to a short one
• adding a Prop 65 warning to a product that does not need one "to be safe", which can confuse buyers and conflict with the label
• leaving the Prop 65 warning off one marketplace while it appears on another

A Prop 65 warning is a statement about a product, and like any claim it rests on facts: what the product contains and how much, which the maker, the supplier or a laboratory test establishes.

Must the Prop 65 warning on the label and the listing match?

Yes. A warning on the package and a different warning, or none, on the listing tells a buyer two different things about the same product. Four things keep the label and listing identical:

• The same signal word. If the label says CA WARNING, the listing says CA WARNING too.
• The same chemical. If the label names a chemical, the listing names the same chemical.
• The same variation. One colour of a product may need a Prop 65 warning when another does not, if the materials differ, so check each variation.
• The same timing. When the label changes, the listing changes, within the 60 days the transition allows.

What should a seller ask before listing a product in California?

Three questions settle most Prop 65 cases before a first listing that will ship to California:

1. Does the package or the supplier's documentation include a Prop 65 warning?
2. If yes, what is the warning's exact text?
3. If no, has the supplier confirmed in writing that no warning is needed?

Write down the answers with the date. The answers are the basis for every listing of that product.

How do marketplaces and Shopify stores handle Prop 65?

Marketplaces handle Prop 65 differently, and their fields change, so check each marketplace's listing form.

A Shopify store is a website selling to California, so the online Prop 65 rules apply to its product pages directly. Testing and compliance firms note that the 2025 changes affect manufacturers and retailers both, so keep the conversation with suppliers open. Ask suppliers to tell you whenever a warning changes, and write that into your purchase terms.

How does a seller update listings when a supplier changes the warning?

A made-up example shows the update. A seller lists a set of kitchen utensils on Amazon, Walmart and a Shopify store. In March, the supplier writes to say the packaging now carries a new short-form Prop 65 warning naming a chemical, replacing the old short form. The seller:

1. Records the supplier's notice with its date. During the transition, internet retailers have 60 days from such a notice to update website warnings.
2. Copies the new warning exactly, signal word and chemical included.
3. Updates each marketplace's Prop 65 field and any place the warning appears in the listing.
4. Updates the Shopify product page, where the warning sits on the page before the add-to-basket button.
5. Replaces the label photo with a photo of the new packaging.
6. Notes the date each listing was updated.

The update takes two weeks at most, and leaves a record showing it was done within the 60 days.

What Prop 65 records should a seller keep?

Prop 65 questions can arrive long after a sale. Keep, for each product:

• the supplier's statement on whether a Prop 65 warning is needed, and its exact text
• any laboratory reports behind the statement
• the dates each listing showed each version of the warning
• notices of change, with the date received

A Prop 65 checklist for online listings

1. Ask the maker or supplier whether the product carries a Prop 65 warning.
2. Get the exact text, signal word and named chemical.
3. Put the warning on the product page, behind a clearly marked WARNING link, or in a prominent warning before purchase.
4. Fill each marketplace's Prop 65 field from the label.
5. Keep the listing and the label in step; update within 60 days of a change notice during the transition.
6. Keep a record of what you were told and when.
7. Check each variation separately, as materials can differ between colours or sizes.
8. Review the warnings on your best sellers once a year, and whenever a supplier changes.

How Commicorn helps

• Your label, as printed. On the Untouched product route the pixels of your photo are never redrawn, so the warning on your package stays exactly as printed.

Commicorn never redraws the warning on your label when you choose Untouched product. Start free.

Questions sellers ask

Does my product need a Prop 65 warning online if the package has none?

Not because of the listing alone: the online Prop 65 warning follows the product's warning. A seller who believes a product should carry one should raise it with the maker or supplier.

Can I still use the old Prop 65 short-form warning?

Yes, during the transition to 1 January 2028, when the older short form without a named chemical is still treated as clear and reasonable. Match the listing to the label the product carries.

Do I need a Prop 65 warning for buyers outside California?

Prop 65 is a California law. Many sellers show the warning on every listing for simplicity, which is a business choice, and where a marketplace's field asks only about California, answer that question.

How quickly must I update a listing when my supplier changes the Prop 65 warning?

During the transition, internet retailers have 60 days after notice from the manufacturer or distributor to update website warnings.

Can a Prop 65 warning sit behind a link instead of on the page?

Yes. Since 1 January 2025, an online Prop 65 warning can be given through a clearly marked hyperlink on the product page using WARNING, CA WARNING or CALIFORNIA WARNING.