---
title: "SW01001: Invalid property prefix"
description: "The prefix, tailwindPrefix, or themePrefix setting does not start with -- and end with -."
image: "https://stillwind.dev/og.png"
---

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# SW01001: Invalid property prefix

This error occurs when `prefix`, `tailwindPrefix`, or `themePrefix` is not a valid prefix for
custom properties. A prefix must start with `--`, end with `-`, and contain no
whitespace. The message names the setting.

## Reported

**stillwind.config.ts**

```ts
import { defineConfig } from "stillwind/config";

export default defineConfig({
  projects: [
    {
      css: "./src/stillwind.css",
      files: ["src/**/*.tsx"],
      prefix: "sw",
    },
  ],
});
```

> SW01001: prefix must start with `--` and end with `-`

## Fixed

```ts title="stillwind.config.ts"
import { defineConfig } from "stillwind/config";

export default defineConfig({
  projects: [
    {
      css: "./src/stillwind.css",
      files: ["src/**/*.tsx"],
      prefix: "--sw-",
    },
  ],
});
```

## How to fix

- Add `--` at the start and `-` at the end, as in the example.
- Use the same value in client and server builds that share styles.

Source: https://stillwind.dev/docs/errors/SW01001/index.mdx