Why I Cannot apply unknown utility class `border-border`? CssSyntaxError: tailwindcss [duplicate]

Question

This is my global.css

@import "tailwindcss";

@layer base {
  :root {
    --background: 0 0% 100%;
    --foreground: 222.2 84% 4.9%;
    --card: 0 0% 100%;
    --card-foreground: 222.2 84% 4.9%;
    --popover: 0 0% 100%;
    --popover-foreground: 222.2 84% 4.9%;
    --primary: 221.2 83.2% 53.3%;
    --primary-foreground: 210 40% 98%;
    --secondary: 210 40% 96.1%;
    --secondary-foreground: 222.2 47.4% 11.2%;
    --muted: 210 40% 96.1%;
    --muted-foreground: 215.4 16.3% 46.9%;
    --accent: 210 40% 96.1%;
    --accent-foreground: 222.2 47.4% 11.2%;
    --destructive: 0 84.2% 60.2%;
    --destructive-foreground: 210 40% 98%;
    --border: 214.3 31.8% 91.4%;
    --input: 214.3 31.8% 91.4%;
    --ring: 221.2 83.2% 53.3%;
    --radius: 0.5rem;
  }

  .dark {
    --background: 222.2 84% 4.9%;
    --foreground: 210 40% 98%;
    --card: 222.2 84% 4.9%;
    --card-foreground: 210 40% 98%;
    --popover: 222.2 84% 4.9%;
    --popover-foreground: 210 40% 98%;
    --primary: 217.2 91.2% 59.8%;
    --primary-foreground: 222.2 47.4% 11.2%;
    --secondary: 217.2 32.6% 17.5%;
    --secondary-foreground: 210 40% 98%;
    --muted: 217.2 32.6% 17.5%;
    --muted-foreground: 215 20.2% 65.1%;
    --accent: 217.2 32.6% 17.5%;
    --accent-foreground: 210 40% 98%;
    --destructive: 0 62.8% 30.6%;
    --destructive-foreground: 210 40% 98%;
    --border: 217.2 32.6% 17.5%;
    --input: 217.2 32.6% 17.5%;
    --ring: 224.3 76.3% 48%;
  }
}

@layer base {
  .border-border {
    border-width: 2px;
    border-color: var(--color-red-500);
  }
}

@layer utilities {
  .animate-pulse-slow {
    animation: pulse 3s cubic-bezier(0.4, 0, 0.6, 1) infinite;
  }

  .delay-75 {
    animation-delay: 75ms;
  }

  .delay-150 {
    animation-delay: 150ms;
  }
}

I run npm run dev, got error:

CssSyntaxError: tailwindcss: Cannot apply unknown utility class border-border

Why?

--color-red-500 is not defined anywhere in your :root variables.? — Omprakash S
– Omprakash S, Commented Nov 5 at 8:47
The @import statement is the first line of the provided code. Colors are provided by Tailwind CSS. — Wongjn
– Wongjn, Commented Nov 5 at 8:55
In the main question on this topic, you can find many good answers for v3 and v4 too. — rozsazoltan
– rozsazoltan, Commented Nov 5 at 9:17

Wongjn · Accepted Answer · 2025-11-05 08:54:30Z

4

This error is because the utility class name border-border does not exist with your configuration of Tailwind but you have tried to use it with @apply.

border-* is a group of class names, either used for border-width or border-color. In either case, there is no border value with the default configuration that you are using.

To fix this, you could:

Define `border` as a value

@import "tailwindcss";

@theme {
  --color-border: var(--border);
}

…

Whereever you have @apply border-border, use @reference to reference this CSS file:

@reference "../path/to/global.css";

selector {
  @apply border-border;
}

Replace `@apply`

selector {
  border-color: var(--border);
}

answered Nov 5 at 8:54

Wongjn

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Why I Cannot apply unknown utility class `border-border`? CssSyntaxError: tailwindcss [duplicate]

1 Answer 1

Define `border` as a value

Replace `@apply`

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1 Answer 1

Define border as a value

Replace @apply

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Define `border` as a value

Replace `@apply`