Whatnot vs Mercari

Whatnot and Mercari both land on Depends.

Whatnot

Depends

Confidence: Medium

Buy if you're a collectibles seller wanting a built-in live auction audience, or a shopper who enjoys livestream bidding and accepts markups.

Depends

Confidence: Medium

Use it if you casually buy or sell secondhand items and accept a flat 10% fee plus imperfect support.

Whatnot versus Mercari
Compare	Whatnot	Mercari
Verdict	Depends	Depends
Best for	Collectibles and trading-card sellers	Casual sellers clearing closets
Who it's not for	Bargain hunters . auction hype often pushes prices above retail	High-volume professional resellers
Privacy	No public CVEs found; runs a HackerOne bug bounty; user reports of unauthorized charges and past shill bidding remain the main concerns.¹²	Legitimate service overall, but two improper-authorization CVEs (CVSS 7.5) and a 2021 Codecov-linked data breach are on record.
Support quality	Widespread support complaints across Reddit.	Trustpilot and BBB report unhelpful support
Public sentiment	Sentiment is split: many buyers and sellers enjoy the platform, while recurring complaints target support, fees, and buyer protection.	Users like the app's simplicity and authentication, but many complain about fee changes, support quality, and seller treatment.¹⁶
Biggest gotcha	Fees stack: 8% commission plus processing . roughly $22.10 taken from a $200 sale^³	New fee structure since January 2025 added buyer fees; some sellers say it's no longer worth cross-posting¹⁵