A single input in a form can submit

Today I learned that if you have a single text field in a form then browsers will automatically submit it when you press enter.

<form>
  <label>
    Search
    <input type="text">
  </label>
</form>

This is kinda handy since normally you need to add a submit button to be able to submit a form — but, you should be aware that if you add another field then you do need to add a submit button for the form to work.

This post goes into more detail.