svelte-check

The svelte-check checker runs svelte-check, which reports type errors, Svelte compiler warnings, and accessibility warnings in Svelte components and .ts files.

Set up

1. Install svelte-check (version 4 or later) and TypeScript:

   pnpm

   pnpm add -D svelte-check typescript

   npm

   npm install -D svelte-check typescript

   yarn

   yarn add -D svelte-check typescript

   bun

   bun add -d svelte-check typescript

2. Enable the checker:

   checker({
     svelteCheck: true,
   })

In dev mode, the checker runs svelte-check --watch from the Vite root. In build mode, it runs svelte-check.

Pass flags to svelte-check

Use flags to pass svelte-check CLI flags, for example to choose a tsconfig:

checker({
  svelteCheck: {
    flags: '--tsconfig ./tsconfig.app.json',
  },
})

In dev mode, the checker manages --watch, --preserveWatchOutput, and --output itself, so those flags only apply in build mode. --workspace applies in both modes and defaults to the Vite root.

Options

Option	Type	Default	Description
flags	string	''	CLI flags for svelte-check.
dev.logLevel	('error' | 'warning')[]	['error', 'warning']	Diagnostic levels to report in dev mode.