What endpoint should I use in Svelte?

Svelte apps submit to DropForm using POST https://api.dropform.app/s/{uid}, where {uid} identifies your form.

Should I use FormData or JSON in Svelte?

Use FormData for easiest integration and file uploads. Use JSON if you don’t upload files and prefer a pure JSON request.

How do I force JSON response for multipart uploads?

Include a multipart part named 'data' with Content-Type application/json. DropForm detects this and returns JSON instead of a redirect.

DropForm with Svelte

Integrate DropForm into a Svelte app using fetch. Includes basic form submit, loading state, inline errors, and file uploads.

January 16, 2026 by DropForm Team

This guide shows how to submit forms to DropForm from Svelte using the Submission API endpoint: POST https://api.dropform.app/s/{uid}.

You’ll learn:

how to submit with fetch + FormData
how to show loading + success/error messages
how to upload files (multipart)
how to force multipart JSON mode (optional)

What you need

Your form endpoint: https://api.dropform.app/s/{uid}
A Svelte app (SvelteKit or Svelte SPA)

Svelte example (fetch + FormData)

The recommended approach is using FormData. It works for both text fields and file uploads, and you should not set the Content-Type header manually.

Example component

JSON mode (optional)

If your form doesn’t upload files and you want a pure JSON request, send application/json.

Example: submit JSON

File uploads

File uploads are automatic with FormData. If you want to guarantee a JSON response for multipart uploads, include a data part with Content-Type: application/json.

Example: force multipart JSON mode (optional)

Common gotchas

Do not set Content-Type for FormData: the browser sets the multipart boundary.
Prefer FormData for file uploads: JSON cannot include raw files.
Handle 400 errors: DropForm returns JSON describing validation errors in JSON mode.