Combinations & Default Combination Handling
Control how product combinations (size, colour, material variants) appear in your Facebook catalogue — as individual variant entries, as a single representative product, or as a plain simple product.
Available since v2.0.2
Overview
In PrestaShop, a product with attributes (e.g. a T-shirt in sizes S, M, L) has one parent product and multiple combinations. Facebook's catalogue format treats these as a product group: each combination becomes a separate item that shares an item_group_id pointing back to the parent.
When you export combinations, your catalogue grows proportionally — a product with 10 size-colour combinations produces 10 catalogue entries. This gives Facebook accurate stock and pricing per variant, but it also means catalogue size increases significantly for stores with many attribute combinations.
If you disable combination output, each product appears as a single entry using the parent product's data. You can optionally enrich that single entry with the default combination's attributes (stock, price impact, reference) using the Use default combination data setting.
Configuration
Go to Modules > Module Manager > Facebook & Instagram Product Catalogue Feed Pro > Configure, then open the Product Options tab.
| Field | Values | Default | Description |
|---|---|---|---|
| Generate Product Combinations | Yes / No | No | When enabled, each combination is exported as a separate item with its own g:id and a shared g:item_group_id. When disabled, only the parent product (or the default combination — see below) is exported as a single entry. |
| Combination ID Prefix | Text string (e.g. V) | (empty) | A separator inserted between the product ID and the combination attribute ID when building each combination's g:id. Required when combination IDs would otherwise collide with product IDs elsewhere in the catalogue. |
| Use default combination data if available | Yes / No | No | Only takes effect when Generate Product Combinations is disabled. When enabled, the single catalogue entry for a product with combinations uses the default combination's stock, price, and reference. When disabled, the entry uses the base product data without any combination specifics. |
The Combination ID Prefix field has no effect unless Generate Product Combinations is enabled.
How It Works
Combinations enabled
When Generate Product Combinations is set to Yes, the feed outputs one entry per combination. Each entry carries:
g:id— built as{prefix}{product_id}{combination_prefix}{combination_attribute_id}{suffix}. If the combination has its own reference and your identifier type is set to reference, the combination's reference is used directly instead.g:item_group_id— always the parent product's identifier (product ID or product reference, matching the identifier type setting). This is what tells Facebook that all these entries belong to the same product group.
Stock, price, images, colour, size, and material fields all come from the individual combination, so buyers see accurate data for each variant.
If your combination attributes IDs overlap with product IDs in your catalogue, add a Combination ID Prefix (for example
V) to ensure everyg:idis unique across your entire feed.
Combinations disabled — without default combination data
When Generate Product Combinations is set to No and Use default combination data is also No, each product with combinations is exported as a plain parent product entry. The combination's specific attributes (size, colour, stock per variant) are not reflected. The product reference, price, and stock are those of the parent record.
This mode is the most compact but loses per-variant accuracy.
Combinations disabled — with default combination data
When Generate Product Combinations is set to No and Use default combination data is set to Yes, the feed still outputs a single entry per product, but that entry uses the default combination's data. The g:id is the plain product ID (no combination prefix or attribute ID), and no g:item_group_id is emitted — it reads as a simple product, not a variant.
The practical effect: the price, stock, and reference reflect your default combination rather than the base product. This is useful when the base product itself has a price of zero and all value comes from its combinations, or when the default combination is the only variant you typically have in stock.
Usage Examples
Example: Fashion store with size variants
You sell jeans in sizes 28–38 (6 sizes) and 50 products. Enabling combinations produces up to 300 feed entries. Each entry has its own stock level and links directly to the pre-selected size on your product page. Facebook can show "only 2 left" for a specific size. Recommended for any store where variant-level stock is meaningful to buyers.
Add V as the combination prefix to get IDs like 42V5, 42V6, 42V7, so they never collide with your product ID 42.
Example: Single-SKU store using combinations only for pricing
You use PrestaShop combinations purely to manage purchase prices or supplier references but never show them to customers. Set Generate Product Combinations to No and Use default combination data to Yes. Each product appears as a single entry with the default combination's correct price and reference, keeping your catalogue lean.
Example: Large catalogue where combinations would cause upload timeouts
You have 2,000 products each with 5 combinations — that is 10,000 potential entries. If feed generation is slow or Facebook is hitting a size limit, disabling combination output reduces the feed to 2,000 entries. You sacrifice per-variant data but gain reliability. Pair with a longer cron interval to stay current.
Important Notes
g:item_group_idis only written to the feed when Generate Product Combinations is enabled. When you use the default combination fallback, nog:item_group_idis emitted — Facebook treats it as a standalone product, not a variant.- The Combination ID Prefix applies only to combination entries. The prefix set in Product ID Prefix applies to all products regardless of combination mode.
- Out-of-stock combinations are skipped unless Include out-of-stock products is enabled. The default combination is subject to the same stock check: if it is out of stock and the product cannot be sold when out of stock, it will not appear even in default-combo mode.
- These settings apply globally across all shops and all feed languages. Per-shop combination configuration is not supported.
- Changing this setting requires regenerating the feed before the change is visible in Facebook Commerce Manager.
Troubleshooting
| Problem | Solution |
|---|---|
Facebook reports duplicate g:id values after enabling combinations | Add a Combination ID Prefix to separate combination IDs from product IDs. A single character like V or - is sufficient. |
| Catalogue has fewer items than expected after enabling combinations | Out-of-stock combinations are excluded by default. Enable Include out-of-stock products in the Product Options tab, or check that your combinations have stock assigned in PrestaShop. |
| Default combination data is not appearing despite enabling the option | Confirm that Generate Product Combinations is set to No — the default combination fallback only activates when combination output is disabled. |
All combinations share the same g:item_group_id but Facebook still shows them as separate products | This is correct behaviour. Facebook groups by item_group_id automatically; no extra setup is needed in Commerce Manager. |
| Price in the feed does not match the combination's price | Verify the Include taxes in price setting in Product Options. Also check whether the combination has a price impact set in PrestaShop. |
Frequently Asked Questions
What is item_group_id used for?
It is the field Facebook uses to link all variants of a product together in the catalogue. All combinations of the same product share the same item_group_id, which matches the parent product's identifier. This lets Facebook display a single product listing with a variant selector rather than separate unrelated products.
Will enabling combinations cause my catalogue to be much larger?
Yes. Every enabled combination generates a separate catalogue entry. A product with 10 combinations becomes 10 entries. If you have large numbers of combinations and your feed generation is slow, consider whether per-variant data is necessary for your advertising goals before enabling this option.
Do I always need a Combination ID Prefix?
You need one only if your combination attribute IDs could collide with product IDs elsewhere in your catalogue. In practice, any store with a reasonably large catalogue should add a prefix as a precaution. If your catalogue has 500 products and each product has at most 20 combinations, there is a real risk of overlap without a prefix.
If I use Reference as my product identifier type, does the combination reference get used?
Yes, provided the combination itself has a reference set in PrestaShop. If the combination has no reference, the module falls back to the numeric format {prefix}{product_id}{combination_prefix}{attribute_id}{suffix}.
Can I show only the default combination instead of all variants?
Yes. Set Generate Product Combinations to No and Use default combination data to Yes. The feed will output one entry per product using the default combination's price, stock, and reference without the variant overhead.
Does the default combination fallback emit item_group_id?
No. When using the default combination fallback mode, the entry has a plain g:id (the product's own ID) and no g:item_group_id. Facebook treats it as a standalone product, not as part of a variant group.