Card Guru
Description:
Deal ratings for trading card listings on eBay.
Open an eBay listing, click the Card Guru icon, and it compares the listing to every other Buy It Now listing for the same card. It gives the listing a rating from Great Deal to Overpriced, shows the median asking price, and lists the cheapest copies of the same card on eBay right now.
Card Guru reads the grader and grade, rookie, auto, and serial number from the listing title so it only compares the same card (a PSA 10 is not compared to a raw copy). The eBay search runs on a small Supabase server so the eBay API keys never ship with the extension.
Screenshots:
Cost to setup
Total Cost: $0.00 - Already had the Google Developer Account from TuffFit, and the eBay Developer Program and Supabase free tier cost nothing
Privacy Policy
Card Guru (Chrome extension)
Effective: October 2026
What it reads. Only when you click the Card Guru icon, the extension reads the eBay listing page in your current tab: the item title, price, shipping cost, condition, item number, and image link. It does not read other tabs, run in the background, or access your browsing history.
What it sends. The listing title and item number are sent to Card Guru’s server (hosted on Supabase), which searches eBay’s public listings for the same card using eBay’s official API. The results are sent back to the extension and displayed.
What it stores. Nothing. Listing details and eBay search results are used only to show the current rating and are not saved by the extension or the server. The server keeps short-lived technical logs (such as errors) for troubleshooting, which are deleted automatically.
eBay accounts. Card Guru never asks you to sign in to eBay and does not collect eBay usernames, passwords, purchase history, or other eBay account information. Seller usernames shown in the extension come from public eBay listings and are not stored. Card Guru receives eBay’s Marketplace Account Deletion notifications and, since it stores no eBay user data, has nothing to delete.
No selling or sharing. Data is not sold, rented, or used for advertising, and is used only to provide the extension’s features. Card Guru’s use of data complies with the Chrome Web Store User Data Policy, including the Limited Use requirements.
Affiliate links. Links to eBay listings in Card Guru are eBay Partner Network affiliate links. If you click one and buy, Card Guru may earn a commission from eBay at no extra cost to you. When you click, eBay may set cookies to track the referral; this is covered by the eBay Privacy Notice. Card Guru does not change prices, ratings or the order of listings based on commissions.
Not affiliated with eBay. eBay is a trademark of eBay Inc. Card Guru is an independent tool. eBay’s own data practices are described in the eBay Privacy Notice.
Contact. markstinyprojects@gmail.com