How we compare

Data sources

Each hour we read the public product feed of every tracked shop. For WooCommerce shops this is the Store API that the storefront itself uses (products and their variants). Shops on their own platform are read through the JSON endpoint their storefront calls. Shopify shops will be added later through their public/products.json feed. Nothing is entered by hand and no page is scraped.

Matching products to compounds

Shops name the same compound in different ways. We keep a dictionary of canonical compounds with their aliases. Each product is matched to one compound, one form (vial, pen, cartridge, oral, nasal spray or topical) and one strength per unit.

• Some shops use code names. Where we matched a code name ourselves, the listing carries a “code name” tag. Check the listing before you order.
• Bundles of several compounds, unknown products, supplies and anything outside research peptides are left out.
• Products with no stated strength are listed, but only compared where the strength is known.

Pricing

• All prices are shown in EUR including VAT.
• Shops that list prices without VAT get their local VAT rate added (an assumed rate where the shop does not state it). These rows are marked, and the original price is shown on hover.
• Unit price is the pack price divided by the number of units in the pack.
• Price per mg is the unit price divided by the strength of one unit.

Lowest price rules

• Only items in stock can be the lowest price. Sold-out offers stay visible but are greyed out.
• Cross-shop comparisons use single units, so a shop that only sells packs is not compared against a shop that sells single vials.
• Packs are compared per unit, never by pack price.

Price index

The price index of a shop is the mean of its own price divided by the lowest price, taken over every spec (compound, form and strength) that at least two shops sell in stock. An index of 1.00 means the shop is always the cheapest. It is only shown once a shop shares at least three specs with other shops.

Freshness

Prices are synced every hour and each snapshot is stored with its time. If a shop fails to respond, or returns far less than before, we keep its earlier prices, mark the shop as stale and show a notice. A failing shop never empties the site.

Data and crawler

Our sync identifies itself with this user agent:

PeptilyzeBot/1.0 (+https://peptilyze.com/about/#crawler)

It makes one series of requests per shop per hour and reads only the public Store API endpoints the storefront itself uses. It does not log in, add anything to a cart or load rendered pages.

Shop owners who want a listing corrected or removed can contact us via the address that will be published on the imprint page.

Editorial independence

There is no paid ranking. Order is decided by price, stock and the rules above. Outbound links to shops are marked nofollow sponsored as a precaution.