HTML File Input — Upload Field Reference and Patterns

<form action="https://splitforms.com/api/submit"
      method="POST"
      enctype="multipart/form-data">
  <input type="hidden" name="access_key" value="YOUR_ACCESS_KEY" />

  <!-- Single file, restricted to images -->
  <label>
    Profile photo
    <input name="photo" type="file" accept="image/*" required />
  </label>

  <!-- Multiple files, restricted to PDF/Word -->
  <label>
    Supporting documents (PDF or Word)
    <input name="docs" type="file" accept=".pdf,.doc,.docx" multiple />
  </label>

  <!-- Capture from device camera (mobile) -->
  <label>
    Receipt photo
    <input name="receipt" type="file" accept="image/*" capture="environment" />
  </label>

  <button type="submit">Upload</button>
</form>

The HTML file input is `<input type="file">`. Clicking it opens the OS file picker; selected files are attached to the form on submission. For the upload to actually work, the parent form must have `enctype="multipart/form-data"` — this is the most-forgotten step that silently breaks file uploads.

The `accept` attribute filters the file picker by MIME type or file extension. `accept="image/*"` shows only images; `accept=".pdf,.doc,.docx"` shows only those specific extensions. accept is advisory — it doesn't enforce types server-side. Always validate file types again on the backend.

The `multiple` attribute allows selecting multiple files in one upload. The submitted value becomes a `File[]`. The `capture` attribute (mobile only) tells the device to open the camera directly: `capture="environment"` for rear camera, `capture="user"` for selfie camera. Useful for receipt uploads where you want the camera, not the gallery.

splitforms accepts file uploads up to 10 MB per file, 5 files per submission, on every plan including free. Attachments arrive as email attachments AND downloadable files in the dashboard AND signed URLs in webhooks. No separate file-hosting setup required.

enctype=multipart/form-data on the form. The one rule that catches everyone.