Every product on every marketplace sits in one of 45 classes for trademark purposes. Amazon has thousands of browse nodes and Etsy has hundreds of categories, and neither says a word about classes. Here is the mapping for what sellers list most.
Apparel and print on demand
T-shirts, hoodies, hats, socks, baby clothing: class 25. Tote bags and backpacks: class 18. Phone cases: class 9. Mugs, tumblers, water bottles: class 21. Posters, prints, greeting cards, stickers: class 16. Pillows, blankets, towels: class 24. Wall art on canvas: class 16 for prints, 20 for framed décor in some registers.
Home and kitchen
Furniture, mirrors, frames, cushions as décor: class 20. Kitchen tools, cookware, storage containers: class 21. Candles: class 4. Lighting: class 11. Bedding and curtains: class 24. Rugs: class 27.
Beauty and health
Cosmetics, skincare, soap, essential oils for cosmetic use: class 3. Supplements, vitamins, medicated products: class 5. Beauty tools such as brushes and applicators: class 21. Hair styling devices: class 8 or 11 depending on the register.
Electronics and accessories
Chargers, cables, cases, headphones, smart devices, software and apps: class 9. Lighting: class 11. Toys with electronics: class 28.
Books, paper and digital
Printed books, planners, journals, notebooks: class 16. Ebooks, audiobooks, downloadable printables and templates: class 9. Publishing and online courses as a service: class 41.
Jewellery, toys, food
Jewellery and watches: class 14. Toys, games, puzzles, sporting goods: class 28. Coffee, tea, baked goods, confectionery: class 30. Supplements are class 5, not 30.
Store names
Shop names, store names, and brand names used for retail rather than for a product: class 35, checked alongside your goods class.
Using the table
Pick the class for the product, add the class of anything else you sell under the same name, and set both in the checker above. Then open the class page for each one to see how crowded it is and what else sits in it. The class matters more than the spelling: an identical name in a different class is often no conflict at all, and a similar name in the same class is the pattern behind most takedowns.