Celestia promo codes are often restricted by product type, brand, or collection, and some are tied to particular sale events, so not every item in your cart will always qualify. You can usually spot these exclusions by reading the fine print in the offer description and comparing the listed brands or categories to the product pages in your cart.
Celestia-related coupon pages reference offers that apply only to "top items" or specific named products, which indicates that certain promotions target curated collections rather than the entire catalog. Other listings describe "sitewide" savings but still mention exclusions for some brands, categories, or sale items, a pattern that is consistent with many volume merchants.
When you are unsure whether something qualifies, check the product detail page for any note that it is excluded from promotions, then look at the promo wording for phrases like "selected items," "excludes sale," or "excludes certain brands." If items you care about are listed as excluded, it is usually faster to remove those products, apply the code to the qualifying ones, and then decide whether the discount outweighs purchasing the excluded items separately without a promotion.