Market Memory — Privacy Policy

Last updated: 2026-07-27

Market Memory is a browser extension that records the price and listing history of offers on OLX (olx.pl) so you can see how an offer changed over time. This policy describes exactly what the extension collects, what it deliberately does not, and how to have data removed. It is written to match what the code actually does — nothing here is aspirational.

Who we are

Contact: wojtek20052006@gmail.com.

Market Memory is an independent project and is not affiliated with, endorsed by, or sponsored by OLX. The name "OLX" is used only nominatively — to describe the marketplace the extension reads — and no OLX logo or branding is used.

What we collect and send to our server

When you open an OLX offer page, or open your followed-offers page, the extension reads the listing and sends a minimal record of it to our server so it can become part of a shared price-history database. Each record contains:

• Listing data visible on the offer page — price, title, listing URL and ID, category, the listing's own location (the city/region of the offer, not yours), listing parameters, photo count, posting/refresh timestamps, and whether the offer is active or removed.
• A random device identifier. On first run the extension generates a random UUID and stores it locally. It is sent with each submission so we can attribute contributions and rate-limit abuse without accounts. It contains no name, email, or other personal detail, and is not linked to your identity.
• Submission timestamps — when your device recorded a given listing.
• A numeric hash of the description — not the description text. A short, non-reversible number derived from the description (an FNV-1a hash). It lets the shared dataset detect that a description changed, and when, so that signal is shared across devices — while the text itself never leaves your device and cannot be recovered from the hash.

In the language of Firefox's data-collection categories, that is website content (the offer's visible marketplace data) and browsing activity (the specific listing URLs you viewed, with timestamps). Both are declared as required in the extension manifest, because a crowd-sourced price database cannot function if a contributor opts out of sending them.

What stays on your device and is never transmitted

• Listing description text. The extension keeps the description text in local storage so it can show you what changed. The description text never leaves your device. Only a non-reversible numeric hash of it is sent (see above), so the shared dataset can note that a description changed and when — never the words themselves.
• Your local history records for each listing, which the extension reads back to render the card even when offline.

What we do NOT collect

• No account, name, email address, phone number, postal address, or payment information.
• No general browsing history. The extension runs only on olx.pl, and only reads marketplace listing data — never your activity on any other site.
• Nothing from any website other than OLX.

Data minimization

We store the least we can and prefer a hash or diff over retaining content:

• Description text is never sent or retained on the server; only a short, non-reversible numeric hash of it is, and purely to detect that the description changed.
• Snapshots exclude seller identity, photos, and description text.
• No personal identifiers are collected; the device id is a throwaway pseudonym.

How the data is used

Submitted listing records form a shared, public price-history dataset — the point of the extension is that an offer you meet for the first time can still show the price moves other contributors recorded. Records are pseudonymous and aggregated by listing. We do not sell personal data.

Retention and deletion

Price and listing-history events are retained to provide full-lifetime history, which is the product's purpose. Because the backend is event-sourced and keyed by listing ID, any listing's stored history can be deleted on request — see the Takedown & Removal Policy. To clear the copy held on your own device, remove the extension or clear its local storage from your browser.

Changes to this policy

If we change what the extension collects, we will update this document and the data-collection declaration in the extension manifest together, and revise the date above.

Contact

Questions or requests: wojtek20052006@gmail.com.