Short answer: mainly on big marketplaces plus social‑commerce and specialist fashion sites.

Where Filipinos commonly buy clothes online

• Shopee and Lazada — the two largest general marketplaces where apparel is one of the top categories. (tmogroup.asia)
• Zalora — the Philippines’ fashion‑focused e‑commerce site/marketplace for local and international brands. (zalora.com.ph)
• SHEIN (and discount apps like Temu) — popular for very low‑cost, fast‑fashion items. (ecommercedb.com)
• TikTok Shop and other social‑commerce channels — growing fast for fashion through short‑video, livestreams and creator sales. (business.inquirer.net)
• Facebook/Instagram sellers and buy/sell groups — widely used for small sellers, boutique brands and direct purchases. (shopify.com)
• Recommerce / thrift platforms (Carousell, IG ukay sellers) — many Filipinos buy preloved/“ukay” clothing online. (press.carousell.com)
• Official brand & mall apps/sites (Uniqlo, SM Malls Online, major department stores) — used for brand items, click‑&‑collect and guaranteed stock. (faq-ph.uniqlo.com)

Why these options are popular (brief)

• Frequent big sales, vouchers and free‑shipping promos on Shopee/Lazada. (tmogroup.asia)
• Zalora and brand sites offer easier returns and brand authenticity. (zalora.com.ph)
• Social commerce (TikTok/Facebook/IG) combines discovery + impulse buying via videos and livestreams. (business.inquirer.net)

If you want, I can:

• recommend which of these is best for a specific style or budget, or
• show how to compare prices/reviews across them.