This version applied from 1 October 2026 to 4 October 2026. Current version: /privacy

Cart Optimizer for Cardmarket: privacy policy

Last updated 1 October 2026

In short: the extension reads the Cardmarket pages it needs in your own browser, removes your name, address, account name and balance, and sends the rest to its own server to work out a cheaper cart. Nothing is sold, shared for advertising or used for anything else.

Who we are

Cart Optimizer for Cardmarket ("the extension") finds a cheaper cart for your Cardmarket wants list and, when you ask it to, applies it to your Cardmarket cart. It is made by Considered Software, the data controller for what its server receives. Contact: support@considered.software. It is not made by or affiliated with Cardmarket.

What the extension reads

It reads pages on www.cardmarket.com in your own browser, using the session you're already logged in with: your shopping cart, the wants list you pick, your list of wants lists, sellers' offers for your wanted cards, and those cards' public pages. If your cart is empty, it also reads your account's Addresses page, only to learn which country your default shipping address is in. It reads no other website. It never asks for or sees your password, and never touches payment.

What it sends, and to whom

To show how many of your wants your cart fills, as soon as you open its panel, and to work out the cheapest cart, it sends the pages above to the extension's own server (cart-optimizer-api.considered.software), over an encrypted (HTTPS) connection. Before any page leaves your browser, the extension removes your name, street and city, your account name, your account balance, and the page's security tokens. The server removes them again before it stores anything. What remains is what the optimizer needs: the cards, prices, sellers and their shipping, your wants list's rules, the currency you pay in, and the country you ship to.

Those pages also show what Cardmarket shows every visitor about the sellers on them: their usernames, the country they ship from, their ratings and their listings. Some sellers are private individuals. The extension uses this only to compare their offers and shipping, and keeps it only as long as the pages (below).

It also watches for Cardmarket's own cart requests (adding, removing or clearing cards), to update its count of your wants when your cart changes. It only notes that such a request finished, never what was in it, and sends nothing about it.

The server is hosted by Amazon Web Services (AWS) in Frankfurt, Germany. AWS stores and runs it for us and has no other use of it. Email you send to support@considered.software, and our replies, pass through Cloudflare, which forwards our mail, and Microsoft, whose Outlook service holds our inbox; both may handle it outside the UK and EU, under their own safeguards for international transfers. Nothing is sent to anyone else: no analytics, no advertising, no trackers.

What the server keeps, and for how long

The server doesn't know who you are: there are no accounts, and nothing it keeps holds your name, address or Cardmarket account name.

Everything is stored with AWS in Frankfurt, Germany, in the European Union, encrypted at rest.

Who looks at it

The service works on its own: no person reads your pages or run records to plan your cart. We look at a run's pages or record only when you send feedback about it with "include details" ticked, which ties your message to that run, to answer you and fix the problem; when it's needed to keep the service secure (for example, investigating abuse); or when the law requires it. Feedback messages are read, since that's what they're for.

What stays in your browser

Your settings (the wants list you picked, your seller filters and options), and a feedback message you've started writing (with the email you typed, if any), are saved in your browser's extension storage so they're there next time. A run in progress is kept in the browser's session storage until the browser closes. The account name the page shows is used only in memory, to notice when you log out or switch account, and is never saved or sent.

Why we're allowed to use it (the legal basis)

What we don't do

We don't sell or share your data, use it for advertising, or use it for anything other than finding and applying a cheaper cart and improving the extension. We make no automated decisions about you.

The use of information received by the extension adheres to the Chrome Web Store User Data Policy, including the Limited Use requirements.

Your rights

Under the UK and EU GDPR you can ask to see the data we hold about you, to correct it, to delete it, to restrict or object to our use of it, or to receive a copy. Because we don't know who you are, we can find your data only from a run's or a feedback message's reference, or the email you gave with feedback: email support@considered.software with it, and we'll answer within a month. You can also complain to your data protection authority: in the UK, the Information Commission, still known as the ICO (ico.org.uk).

You can stop at any time by removing the extension, which also deletes what it saved in your browser.

Children

The extension isn't intended for children under 13 (under 16 in some EU countries).

What the extension asked you to agree to (version 1)

Added when this version was frozen: the agreement card in extension 0.1.0, which asked for "Agree and continue" before anything was read.

Changes

If this policy changes, the new version will be posted here with a new date. If the extension starts reading, sending or keeping anything new, it will tell you in the extension itself first.