How price compare works

How we collect prices

Every day an automated program (our “price bot”) checks each product we track at each shop. It reads the price, any “was” or RRP price and stock status from the structured product data shops publish for search engines, or from the public product feed some storefronts provide.

• The bot identifies itself as BargainAU-PriceBot and doesn’t pretend to be a browser, except at Coles, Woolworths, which we reach through a third-party scraping service.
• It follows each shop’s robots.txt, including any crawl-delay it sets, and never makes more than one request every two seconds to a shop.
• If a shop asks it to slow down, it waits as asked. If a shop blocks it, we stop checking that shop rather than trying to get around the block. The exception is Coles and Woolworths, which block all automated access; we still follow their robots.txt rules.
• Each shop gets a daily time budget. If a shop asks for slow crawling, some products are checked every second or third day instead of daily, and the page shows when each price was checked.
• Where a page has no structured price data, an AI model may read the page text instead. We only accept its answer if that exact price appears on the page.
• We record a new price point only when the price, “was” price or stock status changes.

How products get added

We start from a list of popular products and find them in each shop’s published sitemap, the index shops provide so search engines can find their products, or, where a sitemap is out of date, in the shop’s category pages. We then read each candidate page and keep it only if it’s the product itself: refurbished, open-box, bundles and accessories are filtered out.

How we match products across shops

The same product often has a different name at every shop, so names alone never decide a match. In order, we use:

1. Barcode (GTIN). If two listings carry the same valid barcode, they’re the same product. Two different barcodes are always treated as different products.
2. Brand plus the manufacturer’s part number, for shops that don’t publish barcodes. The whole part number has to match: “GV-N5070GAMING OC-12GD” never matches the non-OC card, and prices must be close.
3. Review. Anything less certain can be checked by an AI model and a person before it’s added.

A few phones are tracked across colours, because shops price every colour the same; those pages say so. Every other product is one specific variant.

Groceries: Coles, Woolworths and Aldi

Supermarkets mostly sell their own brands, so for everyday staples we compare like for like rather than identical products: each supermarket’s own-brand milk, bread, eggs and so on. Pack sizes differ (Aldi sells flour in 2 kg bags, Coles and Woolworths in 1 kg). Where the packs are the same size the lowest shelf price is cheapest; where they differ, the lowest price per kilo, litre or item, worked out from each product’s pack size, and the page says so. The staples basket only adds up items all three supermarkets sell, priced for the same quantity at each (the smallest pack any of them sells).

Branded products, like Vegemite or Tim Tams, are only compared when the same product in the same size is on sale at more than one supermarket. Prices are the online prices for delivery or click & collect; your local store and weekly specials can differ.

How the bargain verdict works

For each day, we take the lowest in-stock price across the shops we track. Today’s lowest price is then compared with the last 90 days:

• Lowest in N days: today’s price is at or within 0.5% of the lowest we’ve recorded in the window, and at least 3% below the typical (median) price.
• Below usual price: at least 3% below the typical price.
• Usual price: within 3% of the typical price, either way.
• Above usual price: more than 3% above the typical price.
• Collecting history: we have fewer than 28 days of prices, which isn’t enough to judge.

Warnings we show

• “Was” prices we’ve never seen. If a shop’s “was” price is higher than anything we’ve recorded at that shop in the window, we say so. It may have sold at that price before we started tracking, in store or elsewhere.
• Raised before the sale. If a shop put the price up by 5% or more and then, within 45 days, “dropped” it back to roughly where it started, we show both moves with dates so you can judge the discount.

What counts as a deal

The deals page only lists drops measured against prices we recorded ourselves: today’s lowest in-stock price against the typical (median) daily low over the previous two weeks, plus products at the lowest price in our history. Using the median means a price that was pushed up for a few days and then “cut” doesn’t count as a deal. A shop’s “was” price is never used as the starting point.

Price alerts and your watchlist

Your watchlist is saved in your browser only. Price alerts need your email address: we send one confirmation email, start the alert only after you click it, email you once when the target is reached, and include an unsubscribe link in every email.

What price compare can’t tell you

• Prices can change after we check. Always confirm the price at checkout.
• We don’t see in-store-only prices, price-match outcomes, member pricing, coupons or cashback.
• Delivery costs and stock in your area can change the real cost.
• We don’t cover every shop or every product, and automated collection can occasionally record a wrong price. If you spot one, please tell us.

How we make money

Some “Go to shop” links may be affiliate links, so we may earn a commission if you buy. Commissions never change the prices we record, the verdict, or the order of the shop list, which is always sorted by price.

Corrections and opt-outs

Shops that would like us to stop visiting their site can block BargainAU-PriceBot in robots.txt or email [email protected]. We’re also happy to use a product feed instead of visiting pages. We’ll fix reported errors as quickly as we can.