Privacy policy
Last updated: 1 November 2026
Comps for Cardmarket (“Comps”) is a browser extension that shows comparable prices on Cardmarket card pages. It is built so that almost nothing about you leaves your browser.
What Comps reads
On Cardmarket single-card pages (cardmarket.com/en/…/Products/Singles/…), Comps reads the offers already shown on the page: price, card language, condition, foil and similar attributes, and the seller’s name and type. When you’re signed in, it also reads your username from Cardmarket’s account menu, so your own offers are left out of the comparison. It uses all of this in your browser to compute comparable prices. It does not store any of it and does not send it anywhere. Comps makes no requests to Cardmarket and never submits anything on your behalf.
What Comps stores
- Your settings: the copy you usually sell (language, condition, foil and similar), changes per game, your pricing rule and presets. They are stored in Chrome’s sync storage, so if Chrome sync is on, Google syncs them across your devices as part of your Chrome profile. They contain only your Comps preferences.
- A Cardmarket username, only if you type one in settings. It replaces the signed-in name, for when you sell from a different account than the one you browse with. It is stored only on this device and never sent anywhere.
- Your Pro license key, if you bought Pro, with its status and when it was last checked. It is stored only on this device.
What leaves your device
Only license checks, and only to Polar (polar.sh), the payment provider and merchant of record for Comps Pro. Each check contains your Pro license key, Comps’s Polar organization id and the id of the Comps Pro benefit. When you activate a key, Comps also registers this browser with a label such as “Chrome (Comps 0.1.0)”, which you see in Polar’s customer portal, and from then on sends that activation’s id with each check. Checks happen when you activate a key, about every three days while it is valid (also when you open Comps settings and a check is due), and when you press “Check again” in settings. When you remove the key, Comps asks Polar to free this browser’s activation. A key Polar reports as revoked is not checked again.
Comps has no account, no analytics, no tracking and no advertising. It does not sell your data or share it with anyone other than Polar, as described here.
If you click “Report a problem with this page”, your email app opens with a prefilled message containing the page address, the number of offers Comps read and the Comps version. Nothing is sent unless you send that email yourself.
When you buy Pro or email us
Polar sells Comps Pro as reseller and merchant of record, so your purchase is between you and Polar, and Polar’s privacy policy covers it: polar.sh/legal/privacy-policy. Polar shares your email address and order details, and your name if you gave one, with the maker of Comps (“we”, see Contact). We use them only to answer your support requests and to handle refunds and cancellations. If you email us, we use your message and address only to reply.
Legal basis
License checks, and the purchase data Polar shares with us, are needed to provide Pro, which you bought (Art. 6(1)(b) GDPR). We keep purchase records to meet tax and accounting duties (Art. 6(1)(c) GDPR). We reply to your emails because you asked us to, which is in your and our legitimate interest (Art. 6(1)(f) GDPR). You don’t have to enter a license key: without one, Comps works without Pro.
Where your data is processed
Polar is based in the United States and processes license checks and purchase data there and in other countries. It uses the European Commission’s Standard Contractual Clauses for these transfers. Chrome sync is Google’s service, under your Google account’s terms.
How long it’s kept
Data on your device stays until you remove it in settings or uninstall Comps. Polar keeps purchase data under its own policy. We keep purchase records as long as tax law requires, which in Switzerland is up to 10 years, and delete support emails once they’re no longer needed.
Your rights and control
Under the Swiss Federal Act on Data Protection and, if you’re in the EU or EEA, the GDPR, you can ask what data about you we hold, have it corrected, deleted or restricted, receive a copy, and object to its use. Write to the email below. You can also complain to a data protection authority: in Switzerland the Federal Data Protection and Information Commissioner (edoeb.admin.ch), in the EU the authority where you live.
On your device: clear your username in Comps settings, and remove your license key there too (Comps Pro, “Remove the key from this browser”). Uninstalling Comps deletes everything it stored on your device; settings synced by Chrome are removed with the extension’s data.
Chrome Web Store
Comps’s use of the data described here complies with the Chrome Web Store User Data Policy, including its Limited Use requirements.
Changes
If this policy changes, the new version will be published at this address with a new date, and the change will be noted in the extension’s release notes.
Contact
Comps is made by Zeus Studio, the trading name of Matteo Suez, who is responsible for the data described here.
Email: [email protected]