shadcn/ui vs Mantine: a ready design system or your own code

Mantine pays off when you want a complete, maintained design system; shadcn/ui pays off when you want to own the code and the theme. The component count is not the criterion: 119 against 61 says how much the vendor covers, not what maintenance will cost.

The two EneUI catalogue records also measure weight: Mantine holds 1,606,105 bytes of source for 119 components, shadcn/ui 242,735 bytes for 61. Per component that is 13,497 bytes against 3,979, so Mantine writes 3.4 times more code for each component it offers.

The difference you pay for in hours

The conflict on day one

Mantine ships a global stylesheet and a reset. Tailwind ships Preflight unless you turn it off. If Preflight lands after `@mantine/core/styles.css`, Mantine controls lose margins, borders and control heights. The most voted question on the `mantine` tag is about exactly that order.

npm install @mantine/core @mantine/hooks
npm view @mantine/core version

# l'ordine nel bundle: Preflight prima degli stili Mantine
rg -n "@mantine/core/styles.css|tailwindcss" src/main.tsx src/styles.css

# il record di catalogo, non il README
curl -s https://ui.eneawork.it/api/lib/mantine | jq -r .title

Order is controlled at the entry point, not inside the component. If Mantine styles load before Preflight, the Tailwind reset wins on controls and the bug looks like a theme problem.

The test on the real project

• One screen: a form with validation, a dialog and a table. Those three show what a design system is worth.
• One theme: change the primary colour and the border radius under both choices, then count the files touched.
• One upgrade: simulate a major version bump. Mantine asks for a release note, shadcn asks for a diff.

If the theme changes in one file and the screen stays coherent, the copy-paste model holds. If every change sends you back to the vendor documentation, Mantine is already doing that work for you.

When Mantine pays off

Mantine pays off when the product needs many components and the team is small. 119 components with a coherent API, a single provider and one PostCSS preset are less work than 61 components you have to dress by hand. It also pays off when the design is close to the default and nobody asks for a strong visual identity.

The limit to write down

Named limitation of Mantine: the stylesheet is part of the contract. The import order, the PostCSS preset and the provider variables are conditions you keep in every build. If the project also uses Tailwind, that boundary must be documented, or any new entry point can break the controls.

Licences and dependencies

Mantine is MIT, like shadcn/ui, so the licence does not decide. Dependencies do: Mantine brings `@mantine/core`, `@mantine/hooks` and the PostCSS preset, shadcn brings Radix and three utilities. Both require React 18 or later.

The record to start from is /components/lib/shadcn, the comparison is /components/lib/mantine and dashboards live in /components/cat/dashboard. For the general criterion read how to choose a UI library, for the vocabulary UI kit, component library and design system; the measured comparison of alternatives is in alternatives to MUI.