Here are some popular platforms where you can sell your stuff online for free:

1. goroo Classifieds : A website that’s popular for selling clothes, especially trendy and vintage items. Listing is 100% free.
2. Vinted: You can list your clothes for free, and there are no seller fees. Buyers pay for shipping, making it a great option for cost-effective selling.
3. Facebook Marketplace: Free to list and sell. It’s convenient if you want to sell locally without shipping items.
4. Poshmark: While listing is free, Poshmark takes a flat fee of $2.95 for sales under $15, and a 20% commission on sales over $15.
5. Mercari: You can list your items for free, and they charge a 10% fee when the item sells.
6. eBay: Offers free listings up to a certain number of items per month, with final value fees when an item sells.
7. Craigslist: Free to use and great for local sales, though it’s not as fashion-focused as other platforms.
8. OfferUp: Free to list and sell, primarily aimed at local sales, but you can also ship items for an additional fee.

These platforms provide a good mix of free listings and easy access to buyers! Do you have a specific type of clothing you’re looking to sell?