Privacy Policy

Effective date: 2026-05-16 · Last updated: 2026-05-16

This Privacy Policy describes how MercariBoost ("we", "the extension") handles information when you use the MercariBoost Chrome extension. By installing or using the extension, you agree to the practices described here.

Free-launch version. During the current free phase, MercariBoost does not collect payments, does not require account creation, and does not transmit any data to a server we control. All processing happens locally in your browser. The sections covering payment data will be re-added when (and if) the paid tier launches; users will be notified at least 14 days in advance.

1. Who We Are

MercariBoost is a Chrome extension that helps Mercari sellers relist their listings to maintain visibility on the Mercari marketplace. The extension is published by lesteroc15 ("we", "us", "our"). The documents site for the extension is hosted at https://lesteroc15.github.io/mercariboost-site/.

We are not affiliated with, endorsed by, or sponsored by Mercari Inc. or any of its subsidiaries.

2. Information We Collect

The extension is designed to minimize data collection. The free-launch version stores everything locally in your browser; nothing is sent off-device.

2.1 Information stored locally on your device

The following is stored in your browser's local storage (chrome.storage.local) and never leaves your device:

• Listings you have scraped from your Mercari account: titles, descriptions, prices, photo URLs, categories, brands, conditions, sizes, shipping options, and listing URLs
• Your relist history: which items you have relisted and when
• Usage counters: how many relists you have performed in the last 24 hours
• Extension preferences: UI state, notification preferences
• An internal log buffer (the last 1,000 console events from the extension's own code) — kept to make troubleshooting easier. This buffer can be exported manually from the popup if you need to share it for support, but it is never auto-uploaded.

This data is bound to your local browser profile. Uninstalling the extension permanently deletes it.

2.2 Information we do NOT collect

We do not collect, transmit, store, or sell:

• Your Mercari login credentials (we never see them — the extension operates on pages you have already authenticated with Mercari)
• The content of your messages with buyers or other Mercari users
• Browsing data outside mercari.com
• Personal data such as your name, address, phone number, or government identifiers
• Any data from websites other than Mercari
• Any analytics, telemetry, or tracking data — there is no analytics endpoint in the extension

3. How We Use Information

• Listing data is used solely to enable the relist functionality (re-creating a listing with the same content).
• Usage counters power local-only displays of how much you've used the extension.
• We do not use any data for advertising, profiling, or sale to third parties.

4. Sharing Your Information

We do not sell, rent, or trade your information. Because all data is stored locally on your device and never transmitted to us, there is nothing for us to share. Information may be disclosed to legal authorities only when required by valid legal process and in accordance with applicable law (this would apply to information we hold, not to data stored on your local device).

5. Data Retention

Locally stored data persists as long as the extension is installed on your browser. Uninstalling the extension deletes it. Clearing extension storage from chrome://extensions/ → Details → Site settings also deletes it.

6. Your Rights

You can:

• Delete all locally stored data by uninstalling the extension or by clearing the extension's storage in Chrome's extension settings.
• Request information by emailing lesteroc15@gmail.com. We respond within 30 days. Because we do not collect data centrally, requests about specific data will generally be answered by pointing you to the local storage on your device.

EU and UK residents have additional rights under GDPR, including the right to object to processing, the right to data portability, and the right to lodge a complaint with a supervisory authority. California residents have rights under the CCPA. Contact us at lesteroc15@gmail.com to exercise these rights.

7. Security

We use industry-standard security practices:

• All website traffic to the documentation site is served over HTTPS via GitHub Pages
• Local browser storage is sandboxed by Chrome and isolated from other extensions
• The extension performs no network requests of its own apart from downloading the listing photos already-public on Mercari's CDN during a relist operation

No system is perfectly secure. If we become aware of a security incident affecting your data, we will notify affected users without undue delay.

8. Children's Privacy

The extension is not intended for users under 18. We do not knowingly collect data from children. If you believe a minor has used the extension, please contact lesteroc15@gmail.com.

9. Changes to This Policy

We may update this policy from time to time. The "Last updated" date at the top reflects the most recent change. Material changes (including introducing paid tiers, if and when that happens) will be communicated via in-extension notification at least 14 days before they take effect.

10. Contact

Questions about this policy? Email lesteroc15@gmail.com.

MercariBoost is independently developed software. Mercari is a trademark of Mercari Inc. This extension is not affiliated with, endorsed by, or sponsored by Mercari Inc.