Sidekick Tools (formerly Posh Sidekick)
Automation bots and crosslisting for Poshmark, Mercari and Whatnot
Sidekick Tools, formerly Posh Sidekick, is an AI automation and crosslisting app for resellers, sold as iOS, Android and web apps. Its site lists Whatnot as one of seven marketplaces for cross-posting and offers a Whatnot Bot for follows, follow-backs and relisting. The site does not describe an official Whatnot API or partner integration, so the Whatnot feature is a bot and listing tool, not a verified partnership.
Key features
- Cross Poster that publishes listings to seven marketplaces, Whatnot included.
- Whatnot Bot for follows, follow-backs and relisting.
- Bulk Listing Tool to publish and edit many items at once.
- Relister for refreshing older listings, plus a Poshmark sharer.
- Send Offer tool and eBay and Mercari automation.
- AI stock photo creator.
Who it's for
Resellers who want automation on top of crosslisting, especially across Poshmark, Mercari and Whatnot.
Pricing
Cross Posting plans run from $9.99/mo (100 cross-posts) to $44.99/mo (1,000). Automation plans start at $29.99/mo (50 crosslists). Checked 2026-11-06 on poshsidekick.com/pricing; the footer shows only 2026.
Sources
6 comments
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I'm mostly a Poshmark seller and started doing Whatnot shows this summer. Sidekick was already running my sharing, so adding Whatnot as a crosslist target was the easy path. It's on every plan. One thing that annoyed me: sync is one-way. If I fix a price on the marketplace, the app doesn't pick it up, so I make every edit in Sidekick now. Support has answered me within the hour every time though.
@Becca the one-way thing got me too. Edited 40 prices on Posh and then wondered why nothing matched.
Heads up that relisting is capped at 20 a day on every plan, even the expensive ones. Plan your old inventory around that.
Getting my Posh closet onto Whatnot took an evening, and cross-listing has given me very few problems since.
The Whatnot follow-back bot is the part I didn't expect to use daily. Price feels fair.
Ran into duplicate listings that led to a double sale. Had to clean those up by hand.
Alternatives to Sidekick Tools (formerly Posh Sidekick)
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