Privacy Policy

Last updated: October 4, 2026

FlipJuggler is a simple tool: you paste a Mercari book listing, we tell you whether it's worth flipping. There are no accounts and no sign-ups, and we've kept the data we handle to the minimum the checker needs to work. This page explains exactly what that is.

What we collect when you run a check

• The check itself. The listing link, ISBN, or title you submit — plus the price and shipping you enter — is sent to our servers so we can identify the book and produce your verdict.
• A random device ID. Your browser stores a randomly generated ID on your device, and our servers keep a monthly count of how many checks that ID has run. That's how the free plan's 10 checks a month are counted. The ID is not your name, your Mercari account, or anything that identifies you personally.
• Your Pro license key, if you have one. If you enter a key to unlock Pro, it's stored on your device and sent to our payment provider, Whop, to confirm your subscription is active. We don't store your key on our servers.

What stays on your phone

Your Recent checks list — including which books you marked "Bought it" — is stored only in your browser, on your device. It's never uploaded or backed up by us, and clearing your browser's site data deletes it for good.

Payments

Pro subscriptions are sold and processed entirely by Whop. Your card details go to Whop, never to FlipJuggler — we never see or store payment information. Whop's own privacy policy covers how they handle it.

What we don't do

• No advertising trackers and no third-party analytics.
• No selling, renting, or sharing your data with data brokers — there's barely any data to share.
• No accounts, no passwords, and we never ask for your Mercari login.

How long we keep things

Monthly usage counts are kept so we can enforce the free-plan limit fairly. Book pricing data we cache contains no personal information. If you'd like the usage records tied to your device ID deleted, contact us and we'll remove them.

Changes to this policy

If we ever change what we collect, we'll update this page and the date at the top first — before the change takes effect, not after.

Contact

Questions about privacy: support@flipjuggler.com