Unavailability should be clear before someone tries to buy. The page can still help them understand the product, compare another option or ask a question, provided it does not promise an unknown return date.
Show an unambiguous state
Put « unavailable » near the price and variant selector, not only in a note at the bottom. Disable a purchase action that cannot succeed and explain why. If only one size has sold out, do not mark the entire product unavailable; show the status of each option.
Offer an honest next step
If a replenishment date has been confirmed, show it with an update source. Otherwise, say that the date is unknown. Offer a back-in-stock alert only if the team can actually send it and handle contact details under its policy. You may suggest substitutable products, but explain important differences rather than presenting them as exact equivalents.
Keep the page useful if the item returns
Retain specifications, photographs and care information that remain true. A temporary stock shortage does not automatically require deleting the URL or redirecting it to the homepage. If the item is permanently discontinued, state that plainly and point to a genuinely relevant successor or category.
Synchronise every placement
Check lists, cards, site search, the basket, structured data and any feed used by other services. Google says Product data may include availability; it must reflect the visible state and change with it. An accurate page paired with an outdated « in stock » card undermines trust.
Test a real shortage
Open the product from a category, search results and an older shared link. Check the correct variant, message and next action on a phone. The catalogue guide includes this case in prelaunch testing.