Can I use Shopify Functions without Shopify Plus?

The difference that matters when quoting

It is a detail almost nobody mentions and it decides entire projects: with a public app you adapt to its data model, with your own Function you set the model.

If your rule is “10% off above €500”, there are App Store apps that do it and somebody else maintains them. If your rule is “10% off above €500, except on product family X, and only for the Spanish locations, and not stacking with volume pricing”, no public app is going to model it the same way — and that is where Plus stops being a preference.

What you can do without Plus

Rather more than it looks, and it is worth exhausting before changing plan:

• Quantity rules in the catalog: minimum, maximum and increment per variant. That is what forces full-case ordering, without a line of code.
• Volume pricing: price breaks by quantity inside the catalog.
• Native automatic discounts for standard promotions.
• Public apps that carry Functions inside them, for discounts the above cannot hold.

Of the B2B projects that reach me asking for a Function, a good number are solved by the first two.

When there is no alternative

When the rule looks at the whole cart. Quantity rules are per variant: they do not know whether the order reaches €300, whether you are mixing two price tiers, or whether one product requires another. That needs a validation, which means a Function, which means Plus.

If you want to see what one of those validations looks like from the inside before deciding, there is one published with its tests in shopify-checkout-lab and you can poke at it on the home page.