Source from your couch!

Paste or share a Mercari textbook listing, type in its price and shipping, and FlipJuggler identifies the exact edition, compares the listing's total cost — price plus shipping — against current resale prices, and gives you a verdict with your estimated profit after selling fees: FLIP IT, THIN MARGIN, or PASS. You find out before you spend a dollar, not after.

In the Mercari app, open the listing and tap the ⋮ menu in the corner, then Share → More options. On the Sharing text sheet, tap the copy icon at the corner of the text box — that copies the listing's sharing text, title included. (Don't use Mercari's big Copy Link button: it copies only the link, without the title, so the checker can't tell which book it is.) Come back here, tap Paste, add the listing's price and shipping, and tap Check this listing. Installed FlipJuggler on your home screen? That same More options sheet sends the listing straight into the checker box — you just add the price and shipping and tap Check.

Yes — that's the "What's it worth?" check under the checker, for textbooks you already own. Enter the ISBN (or scan the back-cover barcode) and you'll get the going resale value, what you'd net after selling fees, how fast it should sell, a suggested list price, and a ready-to-paste listing title with the edition spelled out. Worth checks count toward your free checks just like verdict checks.

FLIP IT — estimated profit of $15 or more after fees. THIN MARGIN — $0 to $15: real profit, but thin, so a shipping surprise can eat it. PASS — you'd lose money at that price. CAN'T VERIFY — we couldn't pin down the edition or find a reliable resale price, so we show no profit figure rather than guess. THIN and PASS verdicts also show the all-in total that would make the book a FLIP IT, so you know exactly what to offer.

Current-edition textbooks — the ones students need this semester. Nursing, psychology, and the sciences hold their value especially well. Older editions drop fast once a new edition comes out, and loose-leaf or heavily highlighted copies fetch less than clean bound ones, so the checker flags all of that.

Usually the listing never makes the edition clear — no ISBN in the photos, a vague title, a stock photo. One more possibility: it isn't a textbook. FlipJuggler only tracks textbooks — novels, cookbooks, kids' books and other regular books come back CAN'T VERIFY because we don't price them. If it is a textbook, try the manual check under the checker with the book's ISBN plus the listing's price and shipping — the ISBN is on the back cover, above the barcode, and you can scan that barcode with your camera instead of typing it.

10 every month, with full verdicts — no card required. The counter at the top of the checker shows how many you have left. Every way of starting a check counts the same — pasting a link, sharing from Mercari, typing an ISBN, scanning a barcode, or a "What's it worth?" check. But you only ever pay for a book once a month: re-checking the same book — say, at a different price — is always free, and so are replaying a check from your Recent checks list and the three example listings on this page.

Tap "Save this check as a file" on any verdict card — or "Save record" next to a book you've marked Bought it in Recent checks. It downloads a small text file named after the book with everything from the check: what you paid, the resale value and estimated profit, a ready-to-paste listing title, the photo checklist for when the book arrives, and space for your own notes. When you're ready to list it for resale, it's all in one file on your phone.

It takes a few taps inside Whop: after checkout, Whop emails you a claim code — enter it on Whop to finish claiming your purchase. Then open the Whop app or site, go to Library → FlipJuggler Pro, and tap the SOFTWARE button — your license key is on that page. Paste it once into the Unlock Pro panel under the checker and that device gets unlimited checks — no sign-in needed.

Not yet — books and textbooks are live today, and games and cards are in the works. Pro members get new categories first.