To allow user upload a file:

<input type="file" />

Attributes:

multiple : allow multiple files accept: specify the file type (separate by ,)

Ex:

<form>
  <!-- Allow multiple files, only for jpg and png -->
  <input type="file" multiple accept=".jpg, .png" />
  <!-- Allow any image file -->
  <input type="file" accept="image/*" />
</form>