🧩 Real-World SvelteKit Architecture

Production SvelteKit Patterns with Zod

Explore battle-tested patterns: Server Actions with FormData coercion, Discriminated Unions, Cross-Field Refinements, and API Guards.

⚡ SvelteKit Form Actions + fail(400) Flow

In SvelteKit, form submissions transmit standard browser FormData where all values are strings or files (and unchecked checkboxes are omitted). Zod preprocesses and coerces these strings seamlessly before your database query runs.

Simulated Browser Form

Simulated +page.server.ts Action Code

typescript

1export const actions = {
2  default: async ({ request }) => {
3    const data = Object.fromEntries(await request.formData());
4    const parsed = actionSchema.safeParse(data);
5    
6    if (!parsed.success) {
7      return fail(400, {
8        errors: parsed.error.flatten().fieldErrors,
9        values: data
10      });
11    }
12    
13    await db.course.create({ data: parsed.data });
14    return { success: true };
15  }
16};

HTTP Status: 200 (success)

SvelteKit Action Return Value

{
  "message": "Record successfully created in database!",
  "record": {
    "title": "New Svelte 5 Course",
    "price": 49,
    "slug": "new-svelte-5-course",
    "published": true
  }
}