CartRules One in Cart PRO lets you decide which products, categories, tags, brands, shipping classes, product types, or custom taxonomies can go together in the WooCommerce cart. This page covers getting started, how rules work, common setups, and what to check if something isn’t behaving as expected.
Getting started
- Install and activate the plugin like any other WooCommerce extension.
- Go to WooCommerce › Settings › CartRules › One in Cart PRO.
- Click Enter license key and paste the key from My Account › API Keys on this site. This is what unlocks automatic updates.
- Click Add rule to create your first rule.
How a rule works
Every rule has three parts:
- Group by — how products are grouped: category, tag, brand, shipping class, product type, an individual product, or any custom taxonomy your store has.
- Scope — whether the rule applies to every group (“only one category at a time”), or only to the specific groups you pick (“gift cards must be bought alone, everything else can mix”).
- Action — what happens when a customer tries to mix groups that shouldn’t be combined: Block the new product with a message, or Replace the cart (empty it, then add the new product).
The message shown to customers supports two placeholders: {group} (the group already in the cart, or the one being removed) and {exclusive} (whichever group can’t be mixed with anything else). Leave the message field empty to use the built-in default text for that action.
Common setups
- Only one product per order — Group by: Individual products · Scope: every product · Action: Block. Useful for event tickets or made-to-order items.
- Only one category at a time — Group by: Product category · Scope: every category · Action: Block or Replace cart. Useful for stores selling for multiple brands or vendors that need each order to come from a single category.
- Keep a couple of categories exclusive, let everything else mix — Group by: Product category · Scope: selected categories (e.g. “Gift Cards”) · Action: Block. Gift cards or pre-orders must be bought alone; regular products can still combine freely.
- Heavy items ship alone — Group by: Shipping class · Scope: selected class (e.g. “Heavy”) · Action: Replace cart. Keeps shipping costs accurate.
- Keep bundles separate from regular products — Group by: Product type · Scope: selected type (e.g. “Grouped”) · Action: Block.
These same examples are also available directly on the plugin’s own settings page, under “Examples: what should I set up?”.
Works with the Cart and Checkout blocks
Rules are enforced on both the classic cart/checkout shortcodes and the WooCommerce Cart and Checkout blocks (Store API), so it doesn’t matter which one your theme uses.
Using this alongside a free CartRules plugin
If you also run one of the free CartRules plugins (One Category in Cart, One Tag in Cart, One Brand in Cart, One Shipping Class in Cart, or One Product Type in Cart) with its own restriction switched on, PRO’s settings page will show a notice about it. The free plugin’s check always runs first, so if it blocks a product, PRO’s matching rule for that same kind of grouping never gets the chance to run for it, and the customer only sees the free plugin’s message. This isn’t a conflict as such, but it’s worth knowing about if a PRO rule ever seems like it “isn’t firing.”
Troubleshooting
The settings page includes an “Other code affecting the cart” panel, listing anything else on your site (other plugins, your theme, custom snippets) that also hooks into cart validation, with the exact file and line where it’s defined. This is not necessarily a problem, plenty of legitimate extensions hook these same points, but it’s the first place to check if a rule behaves unexpectedly.
Need help?
Get in touch via the support form and we’ll help you out.