Google Shopping for OpenCart: a step-by-step product feed guide

Google Shopping shows your products with a picture and a price right in search, in the Shopping tab and in Performance Max campaigns. To get there, Google needs a product feed: a file with all your products that Merchant Center downloads from your store on a schedule. Here is how to do it right for OpenCart.

1. What the feed must contain

The required fields for every product are:

• id – a unique, permanent product ID. Use the same one you send in your tracking (GA4, Google Ads), or dynamic remarketing will not find the products.
• title and description – the name and description without HTML. Titles are up to 150 characters; put the important words first.
• link and image_link – full URLs of the product page and the main image.
• price – with currency, e.g. 49.00 EUR. In the EU the price includes VAT.
• availability – in_stock or out_of_stock.
• brand and gtin (EAN) or mpn – for manufactured goods. If a product has no such codes (handmade, own brand), send identifier_exists = no.

Also recommended: google_product_category, product_type (the category path in your store), additional images, sale_price with the sale dates, and the shipping weight.

2. Google product categories

Google has its own list of about 5,500 categories. You do not need to pick one for every product: map the top categories of your store and let subcategories inherit them. An accurate category helps Google show the product for the right searches and is required for some groups (apparel, electronics).

3. Variants – sizes and colors

If a product has options (size, color), Google wants each variant as its own item with its own price, availability and image, all joined by the same item_group_id. Apparel also requires color, size, gender and age_group.

4. Adding the feed to Merchant Center

1. Sign in to Google Merchant Center and verify your website.
2. Open Products → Add products → Add from a file.
3. Choose Add a link to your file and paste the feed URL.
4. Set the fetch to daily and save.

After the first fetch, Diagnostics shows errors and warnings. The most common are a missing GTIN, a price that differs from the product page, and images with text or watermarks.

5. Custom labels for campaigns

The fields custom_label_0 to custom_label_4 are invisible to shoppers but let you split products in Google Ads – for example "on sale", price range or margin – so you can bid more on the products that earn more.

6. Common mistakes

• Price mismatch between feed and website – usually because the feed has no VAT or was not refreshed after a sale.
• Sold-out products marked in_stock – the feed should be regenerated at least once a day.
• Different IDs in the feed and in the tracking – remarketing shows empty ads.

Automatic with OCMasters Product Feeds

OCMasters Product Feeds builds feeds for Google, Meta, TikTok, Microsoft, Pazaruvaj.com, Glami and Skroutz from your OpenCart 3 or 4 store: prices with VAT, specials, variants, Google category mapping and custom labels. The feed refreshes itself, and its IDs match OCMasters Complete Marketing.