truediscount

You're on a product page, there's a big discount tag next to a crossed-out price, and you can't tell whether the old price was ever real. Since 2022, EU law has said that when a shop advertises a price cut, the old price it shows must be the lowest price it charged in the previous 30 days. The site cites the rule as Directive 2019/2161 and notes that consumer authorities still find shops inflating that reference price.

truediscount is a free browser extension that checks the claim for you. The developer says the idea came from Black Friday tags that showed big cuts while the shop's own 30-day lowest price showed the item had been cheaper the week before.

On a product page it adds a badge with a verdict. Either the discount holds up against the 30-day low, or it's a case like the site's own example, a "-50%" deal on something that was cheaper last week. Next to the badge is a small graph of every price you've seen for that product.

Beyond the verdict there's a watchlist of tracked products, showing the current price, the 30-day low and the drop from the 30-day high. You can set a target price and get a notification when a visit records a price at or below it. Price history exports to JSON for backup or to CSV for a spreadsheet.

The one limit to understand comes straight from the FAQ: the verdict is based on prices seen in your browser and on what the shop discloses. There's no central price database behind it. If you've never visited a product before, the extension has no 30-day record of its own to compare against, so it's most useful on things you've been watching for a while. Alerts work the same way and fire when one of your own visits records the lower price.

Supported shops include Amazon EU, Zalando, MediaMarkt and Saturn. The list goes on with MediaWorld, Otto, bol.com and Coolblue, plus Lidl, Notino and Euronics Italy. The developer adds eMAG, Allegro, About You and Morele, and says any other shop can be enabled from the popup. An interactive demo on the page lets you type in a sale price and a crossed-out price to see the verdict.

It's free, with no account. Firefox has a one-click install, Chrome and Edge users can download it, and there's a userscript version. It comes from the same GitHub account as the ShrinkWatch EU grocery extension.

The privacy policy in the project's repository says truediscount does not collect, transmit or sell any data. Product name, the product's URL path, price and date are stored locally in your browser.

The FAQ also says the verdict isn't legal advice, and points you to your national consumer authority if you want to report a shop. If you shop on EU sites and like to watch a few things before a sale, it's worth installing early so the price history has time to build.