When I started working on Web stuff around 2005, there were two extremely popular font styles for body copy:

• 10px Verdana
• 11px Arial

Text that is too small takes more time to read. Users may have to lean towards the screen, hold mobile devices closer, squint, or just concentrate more. As designers and developers, we strive to not ask for such extra effort from people who use or read our work.

Hanna Laakso documents the problems for GOV.UK. This is what they landed on:

 <input type="text" inputmode="numeric" pattern="[0-9]*">

The inputmode attribute is pretty great, and we have a deep dive on that.

Phil Nash came to (almost) same exact conclusion, and blogged about improving the experience of a two-factor auth code input on the Twilio blog:

<input
  type="text"
  name="token"
  id="token"
  inputmode="numeric"
  pattern="[0-9]*"
  autocomplete="one-time-code"
/>

That last attribute is interesting and new to me. It means you get this super extra useful experience on browsers that support it: